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Article

Removal of Remazol Red Dyes Using Zeolites-Loaded Nanofibre Coated on Fabric Substrates

by
Siddratul Sarah binti Mohd Hami
1,
Nor Dalila Nor Affandi
1,*,
Liliana Indrie
2,* and
Ahmad Mukifza Harun
3
1
Textile Research Group, Faculty of Applied Sciences, Universiti Teknologi MARA, Shah Alam 40450, Malaysia
2
Department of Textiles, Leather and Industrial Management, University of Oradea, 410087 Oradea, Romania
3
Nano Lab, Faculty Engineering, University Malaysia Sabah, Kota Kinabalu 88400, Malaysia
*
Authors to whom correspondence should be addressed.
Coatings 2024, 14(9), 1155; https://doi.org/10.3390/coatings14091155
Submission received: 29 June 2024 / Revised: 6 September 2024 / Accepted: 6 September 2024 / Published: 8 September 2024
(This article belongs to the Special Issue Advances in Coated Fabrics and Textiles)
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Abstract

:
Nanofibre-based membranes have shown great potential for removing textile wastewater due to their high porosity and surface area. However, nanofibre membranes exhibit lower dye removal efficiency. Hence, this study aims to improve the dye removal performance of nanofibre membranes by incorporating zeolites. The research involved fabricating composite membranes by electrospinning polyvinyl alcohol (PVA) nanofibres incorporated with zeolites. Mechanical strength was enhanced by placing the PVA/zeolite nanofibre membrane between fusible nonwoven interfacing and woven polyester fabric, followed by heat treatment. Morphological analysis revealed the uniform dispersion of zeolite particles within the PVA nanofibres. EDX analysis confirmed the successful incorporation of zeolites into the fibres. Among all membrane samples, the PZ-0.75 membrane exhibited the highest pure water flux (PWF) with approximately 1358.57 L·m−2·min−1 for distilled water and 499.85 L·m−2·min−1 for batik wastewater. Turbidity of batik wastewater increased proportionally with zeolite concentration, with removal rates of 84.79%, 78.8%, 76.96%, and 74.19% for PZ-0.75, PZ-0.5, PZ-0.25, and PVA membranes, respectively. Furthermore, the UV/Vis spectrophotometer demonstrated that dye removal efficiency increased from 2.22% to 8.89% as the zeolite concentration increased from 0% to 0.75%. In addition, the PZ-0.75 membrane effectively removed RR dye at a concentration of 1 mg/L, with an optimal contact time of approximately 60 min. The adsorption mechanism of the PZ-0.75 membrane aligns with the Freundlich model, with an R2 value of 0.983. Overall, this study demonstrates the efficiency of zeolite in the fabric substrates to improve the filtration and adsorption properties for wastewater treatment, particularly in textile industries.

1. Introduction

Malaysia is one of the many producers of batik, which is a traditional industry in Southeast Asia, aside from Indonesia. In the early 2000s, the Malaysian government drew attention to the batik industry and elevated its profile to a global stage. However, the batik industry in Malaysia, which is a cottage textile industry, consumes a large amount of water during the production process [1]. The textile industry is estimated to use the most water compared to any other industry, and almost all wastewater discharge is highly polluted [2,3]. Batik industries in Malaysia are usually small and medium-sized enterprises (SMEs) that discharge their effluent directly into waterways without pretreatment. The effluent from the industry contains contaminants such as dyes, waxes, and heavy metals with high total suspended solids (TSS) content, which can be damaging to the local ecosystem [3,4,5]. Textile industries generally discharge large amounts of colour-containing water during the dyeing process, which causes genotoxic pollutants in water, including many types of mutagenic and carcinogenic components [6]. The decreasing water quality that affects human health has drawn worldwide concern [7]. Therefore, it is important to remove harmful materials from industrial wastewater, such as textile waste products, to protect the environment. There are several conventional methods to remove contaminants from wastewater, such as chemical coagulation, oxidation, and flotation [4]. Filtration or membrane separation is considered the most effective method for removing dye from water [4,8,9]. A composite membrane fabricated by Makarov et al. [10], demonstrated optimal rejection rates of 60% for Orange II and 70% for Remazol dye solution. Meanwhile, Mansor et al. [11] developed a polyethylene oxide/polyaniline (PEO/PANI) composite membrane for the removal of methyl orange (MO) dye and demonstrated dye rejection of 82.5%. In a separate study, Rafieian et al. [12] showed that novel membranes, which are composed of polyethersulfone (PES) as the matrix and amine-functionalised cellulose nanocrystals (CNC) as the addition of nanofiller, can remove up to 99% of direct red dye and have a maximum adsorption capacity of 90% for copper ions. Nanofibre-based membranes have several advantages, such as high porosity, low basis weight, high surface area, controllable pore size, submicron pore size, and continuous-interconnected pores [7,13]. However, nanofibre membrane exhibited lower dye removal efficiency due to its limited capacity to remove dye molecules from aqueous solution [14]. This leaves a knowledge gap in improving the membrane’s dye removal performance. Hence, the current study aims to improve the dye removal performance of nanofibre membranes by incorporating zeolites. This study incorporates zeolites in the polyvinyl alcohol (PVA) nanofibre membrane. The incorporation of zeolites in polymer membranes enhances their adsorption ability. In a study conducted by Hamid et al. [15], zeolite was incorporated into a polysulfone membrane for the adsorption of copper ions. The research demonstrated that metal removal efficiency was influenced by the pH of the solution, with the maximum adsorption occurring at a pH of 5.0 and a maximum copper ion adsorption capacity of 101 mg/g. Another study by Habiba et al. [16] focused on the development of a chitosan/polyvinyl alcohol/zeolite electrospun composite nanofibrous membrane for methyl orange adsorption. The results showed an adsorption capacity of 153 mg/g, with adsorption efficiency declining as the pH level increased. In addition, the resulting nanofibre became less effective at adsorbing methyl orange after several uses. In a separate study, Habiba et al. [17] investigated the adsorption of Cr6+, Fe3+, and Ni2+ using a chitosan/PVA/zeolite nanofibrous composite membrane. The results indicated that the adsorption kinetics for Cr(VI) were controlled by the rate of direct adsorption, while Fe(III) and Ni(II) adsorption followed the Lagergren first-order model [17]. In a study by Radoor et al. [18], a zeolite-based bio-membrane was developed to examine the adsorption of anionic dye (Rh B dye). The study found that the maximum adsorption was achieved with an initial dye concentration of 10 ppm. The adsorption data fit well with the Freundlich isotherm and pseudo-second-order model. The membrane showed a recyclability adsorption capacity of 91% even after six cycles. According to Chen et al. [19], they developed polyacrylonitrile (PAN) nanofibre with functionalised chitosan and protein for treating dye-containing wastewater. The resulting membrane efficiently removed 97% of cationic dye (toluidine blue O) and anionic dye (dye acid orange 7) after 5 consecutive adsorption–desorption cycles.
Zeolites have been reported to provide better ion exchange properties and higher surface area, making them ideal as adsorbents to remove hazardous compounds from water and air [18]. Due to these factors, zeolites-incorporated nanofibres are well accepted for several applications such as filtration and water desalination. The development of PVA/zeolite membrane has been investigated by several studies [20,21,22,23]. However, the applications and fabrication of PVA/zeolite nanofibre composite membranes differ from this study. For example, Takai et al. [21] developed the PVA/zeolite nanofibre membrane using ultrasonication and added Hexafluoroisopropanol (HFIP) to investigate the adsorption of creatine for blood purification. Rad et al. [22] developed the PVA/zeolite nanofibre composite by adding citric acid before electrospinning, with the aim of removing nickel and cadmium from wastewater. Radoor et al. [23] fabricated PVA/sodium alginate/zeolite membranes through the solvent casting method to study the removal of the anionic dye Congo red. The primary goal of the study is to enhance the removal of Remazol Red dye, commonly used in the batik industry, from wastewater by incorporating zeolites into nanofibre membranes. The fabrication of the PVA/zeolite nanofibre composite membrane involved the formation of PVA/zeolite nanofibre membranes. The zeolites were incorporated into PVA nanofibre membranes using electrospinning. The membrane was sandwiched with woven polyester fabric and fusible interfacing fabric and later subjected to heat treatment at 50 °C for 2 min to enhance the fibre bonding at junctions and increase its mechanical strength. The resulting composite membranes were analysed for morphological, elemental analysis, flux, turbidity, and dye removal. The enhanced membranes have potential to be employed as prefiltration wastewater in small and medium-sized enterprises (SMEs) within the textile industry.

2. Materials and Methods

2.1. Materials

The materials used were zeolite powder (zeolite Y, molecular sieves with particle sizes ranging from 3 µm to 149 µm) from Sigma-Aldrich, St. Louis, MO, USA, polyvinyl alcohol (PVA) with a molecular weight of 125,000 from Sigma Adrich, woven polyester fabric, fusible nonwoven interfacing, and distilled water.

2.2. Preparation of PVA Solution and PVA/Zeolite Solution

The PVA and PVA/zeolite solutions were prepared based on the previous study [4]. To make a PVA solution, 12 wt% PVA was diluted in distilled water for 1 h at 80 °C. For PVA/zeolite solution, the 12 wt% of PVA solution and different concentrations of zeolite were mixed at 80 °C for 1 h. The concentrations of zeolite were 0.25 wt%, 0.5 wt%, and 0.75 wt%, respectively. A further increase in zeolite concentration caused clogging at the electrospinning needle, making the PVA/zeolite solution unspinnable through electrospinning. The solutions were then extruded using electrospinning to form nanofibre membranes.

2.3. Formation of Nanofibre Composite Membranes

The electrospinning process of PVA and PVA/zeolite solution is shown in Figure 1. For PVA/zeolite solutions, three types of samples were produced: PZ-0.25, PZ-0.5, and PZ-0.75. In this study, the solutions of PVA and PVA/zeolite were electrospun separately at a voltage of 10 kV. The distance of spinneret to collector was kept constant at 16 cm with 0.2 mL/h of flow rate. The spinning process was performed for 1 h for each sample. Then, each of the PVA nanofibre membranes and PVA/zeolite nanofibre membranes was sandwiched between woven polyester fabric and fusible nonwoven interfacing, with the polyester as the top layer and interfacing as the bottom layer of the membrane (shown in Figure 2). The polyester fabrics and fusible nonwoven interfacing were supplied by Aman Semesta Enterprise. The fabric properties of the woven polyester and nonwoven interfacing are tabulated in Table 1. Then, the layers were heat-treated using a hot press at 50 °C for 2 min as shown in Figure 3. The heat treatment was conducted in accordance to a previous study by Wang et al. (2023) [24] with few alterations which fit to the membrane samples.

2.4. Membrane Characterisation Using Field Emission Scanning Electron Microscope (FESEM) and EDX Mapping

With the measurement of 0.5 cm × 0.5 cm, each sample was cut and was coated with gold for 3–5 min. Then, all the samples were analysed using FESEM-EDX (Jeol, JSM—7600F) under 3000 to 30,000 magnifications at 15 kV. The ImageJ software (https://imagej.net/ij/, accessed on 3rd March 2024) was used to measure the resultant fibre diameter. In total, 50 measurements were taken at random places from each sample. For EDX mapping, the surface of each membrane sample was cleaned and was analysed for the zeolite content.

2.5. Porosity

The porosity parameters are crucial as they determine the amount of fluid that can be held within a material. To study the porosity of nanofibre composite membranes, this research employed image analysis using FESEM to observe the pores in the composites. According to Daraei et al. [25], after obtaining the composite membrane through FESEM imaging, ImageJ software was used to analyse it, as it is capable of measuring the porosity of the membrane by calculating the number of pixels in the image.

2.6. Filtration (Water Flux)

A gravity-driven liquid filtration set was used to determine pure water flux (PWF) of the samples. Each sample was sandwiched between the upper and lower portions of the glass apparatus. The gravity-driven water flux (J) was calculated using Equation (1):
J = V/(A × ∆t)
where V is the permeating water volume in litres, A stands for the sample area (m2), and ∆t stands for the operation time (h) [26].

2.7. Turbidity

The turbidity of dye wastewater from a local batik industry was measured using a turbidity meter. The dye wastewater contains Red Remazol (RR) dye, binder, and other suspended solids. The turbidity of the wastewater both before and after filtration was measured and the turbidity (%) was calculated using Equation (2):
Turbidity (%) = (Ci − Cf)/Ci × 100
where Ci and Cf are the initial and the final turbidity concentration (NTU) before and after filtration, respectively [27].

2.8. Removal of Red Remazol (RR) Dye at Different Dye Concentrations and Contact Time

The dye adsorption process was conducted using a standard procedure [28]. Different operating conditions of the adsorption experiments such as initial dye concentration (ranging from 1 mg/L to 5 mg/L) and contact time (ranging between 10, 20, 30, 40, 60, 80, and 120 min) were studied to determine their effects. The dye concentration was determined by measuring the absorbance value at λmax = 499 nm using a UV/Vis spectrophotometer. The dye removal efficiency was calculated according to Equation (3).
Dye Removal Efficiency (%) = (Co − Ct)/Co × 100
where Co is the initial dye concentration (mg/L) and Ct is the concentration at time t (mg/L) [11].

3. Results and Discussion

3.1. Morphology Analysis of Zeolite-Incorporated PVA Nanofibre Membranes

This study analysed the morphology of PVA nanofibre membranes and PVA nanofibre membranes at different zeolites loading using FESEM imaging at two magnifications, 3k and 30k, as shown in Figure 4a–d. The size of the nanofibres was determined using ImageJ software, and the result is presented in Figure 5. In terms of morphology analysis, zeolite exhibits irregular cubical structures with an approximate size of 5.1 ± 1.86 µm (Figure 4e). Upon incorporation into the PVA solution, the zeolite broke down into fine particles and dispersed uniformly, resulting in a homogeneous white solution for the PVA/zeolite mixture. Without zeolite, a clear homogeneous PVA solution was obtained. The findings revealed that the PVA nanofibres had uniform and smooth fibres with fibre-to-fibre bonding due to heat treatment (Figure 4a).
After the addition of zeolite, the surface of the fibre remained smooth and uniform (Figure 4b–d), suggesting that the zeolite particles would disperse within the PVA nanofibres during electrospinning; occasional beads appeared between the smooth fibres in PZ-0.25, PZ-0.5, and PZ-0.75 membrane samples due to the accumulation of zeolite particles on the fibres. This was similar to a study reported by Lu, et al. (2015) [29], who incorporated zeolites into a PAN nanofibre membrane and observed bead-like structures between the fibre membranes. Fibre-to-fibre bonding was also observed for all the samples, suggesting that the heat treatment formed the inter-fibre binding and fibre-to-fibre bonding.
The EDX analysis of the fibres shows the successful incorporation of zeolites within the fibres (Table 2). As reported by Lu. et al., Si and Na are two important elements in zeolites [29]. Hence, atomic Si and Na were chosen to observe the presence of zeolites in the PVA nanofibres. The EDX result shows the presence of zeolites within the fibrous electrospun PVA membrane. With zeolite loadings of 0.25 wt%, 0.5 wt%, and 0.75 wt%, the elements of Si and Na were observed, confirming the successful incorporation of zeolites within the fibres. Furthermore, the presence of zeolites was found to affect the resulting PVA nanofibres. By incorporating 0.25 wt%, 0.5 wt%, and 0.75 wt% zeolite, the fibre diameter of PVA nanofibres increased by 9.78%, 10.94%, and 13.79%, respectively, compared to PVA nanofibres without zeolites (Figure 5).

3.2. Pure Water Flux of Zeolite-Incorporated PVA Nanofibre Composite Membranes

To determine the wastewater filtration properties of the composite membranes, the pure water flux (PWF) method was used in this study. Two types of liquid or aqueous solutions were used, distilled water and batik wastewater. Pure water flux (PWF) is the volume of water that passes through the membrane per unit time. The PWF of both distilled water and batik wastewater is shown in Figure 6.
In Figure 6, it was evident that the PWF for distilled water increases with an increase in zeolite concentration. The sequence of PWF from lowest to highest was PVA, PZ-0.25, PZ-0.5, and PZ-0.75. The PVA composite membrane had the lowest PWF for distilled water, while PZ-0.75 had the highest PWF, which was 153.58 L·m−2·min−1 and 1358.57 L·m−2·min−1, respectively. This result showed that incorporating 0.75 wt% zeolites in the membrane raised its PWF by 88.70% when compared to PVA. Furthermore, the addition of 0.25 wt% and 0.5 wt% zeolites increased the PWF for distilled water by 81.01% and 84.6%, respectively, compared to the PVA. As the amount of zeolite increases, the porosity (%) (as tabulated in Table 3) also rises, leading to an increase in the PWF for distilled water.
A similar trend was shown for PWF for batik wastewater where the order from lowest to highest was PVA, PZ-0.25, PZ-0.5, and PZ-0.75, which were 217.15 L·m−2·min−1, 445.25 L·m−2·min−1, 456.76 L·m−2·min−1, and 499.85 L·m−2·min−1, respectively. The findings demonstrated that a greater PWF for batik wastewater is caused by an increase in zeolite concentration. The addition of 0.25 wt% zeolite showed a significant increase in the PWF batik wastewater, which was 51.23% when compared to the PVA membrane. The graph showed a slight increase from PZ-0.25 to PZ-0.75. When comparing PVA to PZ-0.5 and PZ-0.75, the PWF for batik wastewater increased by 52.46% and 56.56%, respectively. In addition, the PVA membrane exhibited a higher flux for batik wastewater compared to distilled water. This could be due to the membrane possibly not being fully wetted or having some initial resistance to water flow. In contrast, wastewater may contain dissolved substances that enhance the overall flux.
All the membranes showed a good PWF result as all the membranes have great hydrophilicity. The PWF of distilled water and batik wastewater increased with higher zeolite concentrations. The current study discovered that porosity influenced the flux properties of the membranes. As the concentration of zeolite increased, the resulting fibre diameter also increased. The accumulation of randomly oriented large fibres creates a larger void within the fibrous structures of the membrane. This has led to an increase in the membrane’s porosity. As the membrane porosity increases, it permits a greater flow of distilled water or aqueous solution through the membrane, leading to a higher flux.
Overall, the PWF for batik wastewater was lower than the distilled water, except the PVA membrane. This was due to batik wastewater containing suspended and dissolved solids, which slow down the flow of the wastewater through the composite membranes.

3.3. Turbidity of Dye Wastewater Using Zeolite-Incorporated PVA Nanofibre Composite Membranes

As a part of this study, we investigated the effectiveness of the composite membranes using two distinct methods: measuring their ability to remove suspended solids from wastewater, known as turbidity, and dye removal efficiency. Additionally, we conducted an adsorption analysis for all the composite membranes. Subsequently, the most effective membrane underwent further analysis to gain a deeper understanding on the dye adsorption, contact time, dye concentrations, and adsorption mechanisms.
Turbidity refers to the measurement of the relative clarity of a liquid and is used to determine the amount of light scattered by particles in the water. The wastewater effluent sample used for the turbidity analysis was obtained from a local batik industry.
The results in Figure 7 indicate that the turbidity of batik wastewater effluent increases with an increase in zeolite concentration. The increase in turbidity was due to the increase in zeolite presented in the membrane. As a result, it has been an increase in the adsorption capacity for suspended solids or particles in the wastewater. A similar result was also reported by Khmiri et al. [30], where they used a ceramic flat membrane based on zeolite clay for the removal of indigo blue dye molecules.
In the current study, the turbidity sequence was PZ-0.75, PZ-0.5, PZ-0.25, and PVA, with removal rates of 84.79%, 78.8%, 76.96%, and 74.19% respectively. As expected, the composite membranes composed solely of PVA nanofibres are inadequate for the removal of suspended solids from batik wastewater. When zeolites are introduced into the PVA, the membranes demonstrate the capacity to effectively filter contaminants, including suspended solids from the wastewater. The incorporation of zeolites increases the absorption sites of the PVA membranes, thus enhancing their capability to absorb and remove suspended solids or particles from the wastewater. Consequently, the PVA composite membranes containing zeolites exhibit better performance in turbidity compared to the PVA membranes without zeolites. Zeolites possess a notable cation-exchange capacity, enabling them to selectively adsorb particles present in the wastewater. A similar observation was reported by Salmankhani et al. [31], who discussed the ability of zeolites to serve as a cation-exchange medium for substances and hydrocarbons.

3.4. Dye Removal Using Zeolite-Incorporated PVA Nanofibre Composite Membranes

Figure 8 depicts the dye removal efficiency of the composite membranes. It has been observed that an increase in zeolite concentration leads to a corresponding increase in the removal of dye. The highest dye removal was observed in the filtrate from PZ-0.75, while the lowest was observed in the filtrate from PVA. The incorporation of zeolites resulted in increasing of the adsorption site. In Figure 9, the absorption sites of zeolites absorb Remazol Red (RR) dye from the aqueous solution. When membranes contain high levels of zeolites, they have more absorption sites that can absorb more dye molecules (Figure 10). From the analysis, the current study demonstrates that the introduction of zeolite in the membrane enhances its filtration properties, as the zeolite enables more efficient filtration.
In addition, the adsorption density increases with higher zeolite concentrations. This trend in dye removal can be explained by the overall increase in the specific surface area of the adsorbent, which provides more active sites for exchange [32,33]. It is understandable that the dosage used in this experiment was higher than the one used by Hammoood, et al. [34], who also investigated the adsorption of reactive dye on synthetic zeolite.

3.5. Effects of Initial Dye Concentration on the Dye Removal by PZ-0.75 Composite Membranes

To gain a better understanding on the dye adsorption properties of the composite membranes, the effects of dye concentration and contact time with adsorption were investigated. For the analysis, this study has chosen PZ-0.75 as it had the highest turbidity removal and dye removal. The study examined the adsorption of dye by agitating PZ-0.75 composite membranes in different Remazol Red (RR) dye concentrations, namely 1 g/mL, 2 g/mL, 3 g/mL, 4 g/mL, and 5 g/mL for the same time period of 1 h. The absorbance of the liquid filtrate at different RR dye concentrations is illustrated in Figure 11. The percentage of dye removal across different concentrations was calculated and presented in Figure 12.
From the result, it shows that there was a proportional decrease in dye removal with a corresponding increase in dye concentration from 1 g/mL to 5 g/mL. The dye removal efficiency was found to decrease from 73% to 62% as the concentration increased from 1 g/mL to 5 g/mL. This suggests that the percentage of removal decreased as the concentration of RR increased. Several studies have reported on the dye removal of various adsorbent materials [35,36]. For instance, Zhu et al. [35] found that dye removal decreased to a minimum when the initial dye concentration was increased, particularly when using alkaline white mud as an absorbent. In addition, the composite membranes exhibited good dye removal performance at a concentration of 1 g/mL.

3.6. Effects of Contact Time on RR Dye Removal by PZ-0.75 Composite Membranes

The amount of dye to be absorbed at a certain period is known as contact time. Figure 13 depicts the dye absorption at time intervals of 10, 20, 30, 40, 60, 80, and 120 min at a constant concentration of dye of 1 mg/L. Based on the results, it can be observed that the PZ-0.75 composite membranes started to uptake RR within 60 min. The dye removal efficiency increases from 45% to 74% (Figure 14). At this point, all the adsorption sites were saturated, which indicates that any further contact would not increase the removal of the RR from the solution. This state was maintained for 60 min and, later, the amount of RR desorbing from the composite membranes. Consequently, an equilibrium was established, and the time taken to reach this state is referred to as the equilibrium time, which measures the composite membrane’s maximum adsorption capacity. This finding aligns with the results reported by Hammood et al. [34]. After 60 min, the dye adsorbent decreased, with dye removal efficiency dropping to 66% at 120 min.
Based on the outcomes of the current experiment, the PZ-0.75 membrane was relatively efficient in removing RR dye from aqueous solutions. PZ-0.75 demonstrated effective removal of RR dye at a concentration of 1 mg/L, with the optimal contact time being approximately 60 min.

3.7. Adsorption Mechanism

To understand the adsorption isotherm of the composite membranes, the Freundlich and Langmuir models were used in this study. The Langmuir and Freundlich isotherm equations were adopted from Hammood et al. [34].
The Langmuir adsorption model is based on Equation (4):
Ce/Qe = Ce/Qm + 1/KL Qm
while the Freundlich adsorption model is based on Equation (5):
log Qe = log Kf + 1/n log Ce
where Qe represents the quality of adsorbate adsorbed per unit weight of adsorbent at equilibrium (mg/g), Qm is the highest adsorption capacity of adsorbent, and Ce is the concentration of adsorbate at equilibrium in solution after adsorption (mg.L). Kf is a constant related to bonding energy, KL is the Langmuir constant, and 1/n is the adsorption intensity.
In the Langmuir isotherm, it is assumed that adsorption occurs as a monolayer on a homogeneous adsorbent surface. However, based on the data in Table 4, the adsorption of RR dye by the composite membrane aligns with the Freundlich isotherm.
This indicates that the RR dye adsorption involves interactions between adsorbate molecules on heterogeneous surfaces, leading to multilayer formation. The value of 1/n in the Freundlich constant indicates the validity of the adsorption process. According to Maimulyanti et al. [37], if the 1/n value falls between 0 and 1, it suggests that adsorption capacity increases with increasing dye concentration, with new adsorption sites appearing, making this isotherm model more appropriate. This observation aligns with our results, where the adsorption capacity increased with higher RR concentrations (Figure 15).

4. Conclusions

This study investigated the morphology, elemental analysis, flux, turbidity, dye removal properties, and adsorption mechanism of polyvinyl alcohol (PVA) nanofibre composite membranes and PVA membranes incorporating zeolites. Through FESEM analysis, the study revealed that the PVA nanofibres had uniform and smooth fibres with fibre-to-fibre bonding due to heat treatment. Zeolite particles were observed to disperse uniformly within the PVA nanofibres during electrospinning, despite occasional bead-like structures and fibre-to-fibre bonding remaining in all samples. EDX analysis confirmed the successful incorporation of zeolites into the fibres. The PWF increased with zeolite concentration for both distilled water and batik wastewater, with PZ-0.75 having the highest PWF compared to other samples. The fibre diameter also increased with an increase of zeolite loading from 0.25% to 0.75%, enhancing the membrane porosity and pure water flux (PWF). In addition, the turbidity of batik wastewater increased with higher zeolite concentrations, as zeolites enhanced the adsorption capacity for suspended solids. The study also evaluated dye removal efficiency using a UV/Vis spectrophotometer. The results showed that the 0.75% zeolite concentration resulted in greater dye removal compared to other samples. The analysis further investigated the effects of dye concentration and contact time on adsorption performance, revealing a proportional decrease in removal efficiency with increasing dye concentrations and an equilibrium reached after one hour of contact. The adsorption mechanisms of the PZ-0.75 membrane aligns with the Freundlich model, with an R2 value of 0.983. Overall, the findings demonstrated that increasing the amount of zeolites in PVA nanofibre membranes improves their filtration and adsorption properties, making them more effective for prefiltration wastewater, particularly in industries like textiles. The study highlights the potential of zeolite-based membranes for prefiltration textile wastewater. Further research could explore optimising zeolite concentrations, examining the effects of rheological properties of PVA–zeolite solutions on the stability of fibre spinning, and improving membrane fabrication techniques to enhance performance and scalability for practical applications in wastewater treatment systems.

Author Contributions

Conceptualisation, S.S.b.M.H., N.D.N.A., L.I. and A.M.H.; methodology, S.S.b.M.H., N.D.N.A., L.I. and A.M.H.; software, S.S.b.M.H., N.D.N.A. and L.I.; validation, S.S.b.M.H., N.D.N.A., L.I. and A.M.H.; formal analysis, S.S.b.M.H. and N.D.N.A.; investigation, S.S.b.M.H., N.D.N.A., L.I. and A.M.H.; resources, N.D.N.A., L.I. and A.M.H.; data curation, S.S.b.M.H.; writing—original draft preparation, S.S.b.M.H.; writing—review and editing, N.D.N.A., L.I. and A.M.H.; visualisation, S.S.b.M.H.; supervision, N.D.N.A.; project administration, S.S.b.M.H. and N.D.N.A.; funding acquisition, L.I. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the University of Oradea within the framework of the grant’s competition “Scientific Research of Excellence Related to Priority Areas with Capitalization through Technology Transfer: INO-TRANSFER-UO-2nd Edition” projects no. 232/2022.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Acknowledgments

The authors would like to acknowledge the University of Oradea for providing publication funding and the Faculty of Applied Sciences, Universiti Teknologi MARA, for supporting research activities.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. The schematic view of electrospinning process.
Figure 1. The schematic view of electrospinning process.
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Figure 2. Arrangement of polyester, nanofibre, and nonwoven interfacing.
Figure 2. Arrangement of polyester, nanofibre, and nonwoven interfacing.
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Figure 3. The schematic view of heat treatment.
Figure 3. The schematic view of heat treatment.
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Figure 4. FESEM images of (a) PVA nanofibre membranes, (b) PZ-0.25 membrane, (c) PZ-0.5 membrane, (d) PZ-0.75 membrane, and (e) zeolites.
Figure 4. FESEM images of (a) PVA nanofibre membranes, (b) PZ-0.25 membrane, (c) PZ-0.5 membrane, (d) PZ-0.75 membrane, and (e) zeolites.
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Figure 5. Fibre diameter of heat-treated membrane of different zeolite loadings.
Figure 5. Fibre diameter of heat-treated membrane of different zeolite loadings.
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Figure 6. The effects of zeolite concentration with pure water flux (PWF) of distilled water and wastewater. Some error bars were omitted due to their low values.
Figure 6. The effects of zeolite concentration with pure water flux (PWF) of distilled water and wastewater. Some error bars were omitted due to their low values.
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Figure 7. Turbidity of batik wastewater effluent of different membranes.
Figure 7. Turbidity of batik wastewater effluent of different membranes.
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Figure 8. The dye removal of Remazol Red dye of different composite membranes.
Figure 8. The dye removal of Remazol Red dye of different composite membranes.
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Figure 9. Influence of zeolite concentrations on dye adsorption.
Figure 9. Influence of zeolite concentrations on dye adsorption.
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Figure 10. Remazol Red dye absorption on zeolite.
Figure 10. Remazol Red dye absorption on zeolite.
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Figure 11. UV–vis spectra of liquid filtrate at different dye concentrations.
Figure 11. UV–vis spectra of liquid filtrate at different dye concentrations.
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Figure 12. Dye removal efficiency against initial dye concentration for PZ-0.75.
Figure 12. Dye removal efficiency against initial dye concentration for PZ-0.75.
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Figure 13. Relationship between dye adsorption over the contact time.
Figure 13. Relationship between dye adsorption over the contact time.
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Figure 14. Dye removal efficiency against contact time for PZ-0.75.
Figure 14. Dye removal efficiency against contact time for PZ-0.75.
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Figure 15. Relationship between initial dye concentration and dye adsorption capacity for PZ-0.75.
Figure 15. Relationship between initial dye concentration and dye adsorption capacity for PZ-0.75.
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Table 1. Properties of woven polyester fabric and interfacing used in this study.
Table 1. Properties of woven polyester fabric and interfacing used in this study.
Woven Polyester FabricNonwoven Interfacing
Thickness (mm)1.831.75
Weight (g/m2)110.0734.54
DensityWarp/cmWeft/cm-
≈55≈37-
Table 2. The elemental analysis of atomic% of elements sodium (Na) and silicone (Si) for PVA nanofibre membranes at different zeolite loading.
Table 2. The elemental analysis of atomic% of elements sodium (Na) and silicone (Si) for PVA nanofibre membranes at different zeolite loading.
Atomic %
MembraneNaSiTotal
PZ-0.2568.9131.09100
PZ-0.545.854.2100
PZ-0.7527.6372.37100
Table 3. Porosity of membrane samples at different zeolite loading.
Table 3. Porosity of membrane samples at different zeolite loading.
MembranePorosity (%)
PVA 12.51
PZ-0.2516.47
PZ -0.525.41
PZ-0.7539.07
Table 4. Parameters of isotherm adsorption.
Table 4. Parameters of isotherm adsorption.
Langmuir ConstantFreundlich Constant
KLqmaxR2Kf 1 n R2
0.4543.0520.9790.9490.8280.983
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Hami, S.S.b.M.; Affandi, N.D.N.; Indrie, L.; Harun, A.M. Removal of Remazol Red Dyes Using Zeolites-Loaded Nanofibre Coated on Fabric Substrates. Coatings 2024, 14, 1155. https://doi.org/10.3390/coatings14091155

AMA Style

Hami SSbM, Affandi NDN, Indrie L, Harun AM. Removal of Remazol Red Dyes Using Zeolites-Loaded Nanofibre Coated on Fabric Substrates. Coatings. 2024; 14(9):1155. https://doi.org/10.3390/coatings14091155

Chicago/Turabian Style

Hami, Siddratul Sarah binti Mohd, Nor Dalila Nor Affandi, Liliana Indrie, and Ahmad Mukifza Harun. 2024. "Removal of Remazol Red Dyes Using Zeolites-Loaded Nanofibre Coated on Fabric Substrates" Coatings 14, no. 9: 1155. https://doi.org/10.3390/coatings14091155

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