Search Results (12)

The excessive emission of cadmium (Cd²⁺) poses a serious threat to the aquatic environment due to its high toxicity and bioaccumulation potential. This study constructed three types of vertical-subsurface-flow constructed wetlands configured with iron–carbon–zeolite composite substrates, including an iron–carbon–zeolite constructed wetland (TF-CW), a zeolite–iron–carbon constructed wetland (FT-CW), and an iron–carbon–zeolite mixed constructed wetland (H-CW), to investigate the purification performance and mechanisms of constructed wetlands for cadmium-containing wastewater (0~6 mg/L). The results demonstrated that iron–carbon–zeolite composite substrates significantly enhanced Cd²⁺ removal efficiency (>99%) through synergistic redox-adsorption mechanisms, where the iron–carbon substrate layer dominated Fe-Cd co-precipitation, while the zeolite layer achieved short-term cadmium retention through ion-exchange adsorption. FT-CW exhibited superior NH₄⁺-N removal efficiency (77.66%~92.23%) compared with TF-CW (71.45%~88.05%), while iron–carbon micro-electrolysis effectively inhibited NO₃⁻-N accumulation (<0.1 mg/L). Under cadmium stress, Typha primarily accumulated cadmium through its root systems (>85%) and alleviated oxidative damage by dynamically regulating antioxidative enzyme activity, with the superoxide dismutase (SOD) peak occurring at 3 mg/L Cd²⁺ treatment. Microbial community analysis revealed that iron–carbon substrates promoted the relative abundance of Bacteroidota and Patescibacteria as well as the enrichment of Saccharimonadales, Thauera, and Rhodocyclaceae (genera), enhancing system stability. This study confirms that iron–carbon–zeolite CWs provide an efficient and sustainable technological pathway for heavy metal-contaminated water remediation through multidimensional mechanisms of “chemical immobilization–plant enrichment–microbial metabolism”. Full article

Anaerobically digested liquid pig manure (LPM) is enriched with nutrients and thus can be used as an alternative nutrient source and substitute for chemical fertilizer (CF) in rice (Oryza sativa L.) farming. However, there are concerns regarding the contamination of the surrounding water due to the discharge of ponding water containing dissolved organic carbon (DOC), nitrogen (N), and phosphorus (P) from rice paddies fertilized using LPM. This study investigated the effects of the co-application of fly ash (FA) and zeolite (Z) amendments (FAZ amendments) on the concentration of DOC, N, and P in the ponding water of rice paddies fertilized with LPM at two different rates (standard (LPM_S) and double (LPM_D) at 11 and 22 g N m⁻², respectively). Rice was cultivated using four nutrient treatments, including no input, CF (11 g N m⁻²), LPM_S, and LPM_D, with or without FAZ amendments. When FAZ was not amended, LPM_S and LPM_D application increased the DOC concentration by 32% and 41%, respectively, compared to CF treatments (11 g N m⁻²), reflecting a high DOC concentration in LPM. The total N and P concentrations in the ponding water were lower in LPM_S treatment (by 5 and 8%, respectively) but higher (by 94% and 47%, respectively) in LPM_D treatment compared to CF treatments in the absence of FAZ, indicating a high potential for water pollution with a double LPM application rate. With a given nutrient treatment, FAZ amendments decreased DOC by 15–39%, supporting the immobilization of DOC by Z. FAZ consistently decreased the NH₄⁺ concentration by 6–51% across the nutrient treatments, likely via the sorption of NH₄⁺ onto the negatively charged sites of Z, but its effect on total N concentration was not consistent. Unexpectedly, total P concentration increased (by 77–167%) following the FAZ amendment. FAZ amendments tended to increase rice biomass and grain yield for LPM treatments, but these rice growth parameters were poor compared to CF regardless of FAZ amendment. Our results show that the application of LPM as a complete replacement for CF may hamper rice yield while increasing the likelihood of water pollution with DOC and P, although the co-application of FAZ may help to reduce rice yield loss and decrease DOC and NH₄⁺ concentrations. Full article

Organic agriculture has few tools against pests and diseases and is constantly looking for effective and sustainable products such as geomaterials, i.e., zeolite. This study evaluates the physiological and morphological responses of olive plants (Olea europaea) to foliar applications of different geo-materials, specifically kaolin, natural zeolite, and ammonium-enriched zeolite. The research examines leaf anatomical modifications, including internal tissue structures, trichome and stomatal density, chlorophyll content, and gas exchange parameters, alongside the impact on fruit development and extra virgin olive oil (EVOO) quality. Results indicate that kaolin application negatively influenced transpiration and stomatal conductance, an effect corroborated by increased xylem vessel wall thickness. However, the reduction in stomatal conductance was attributed to a functional rather than morphological adaptation, as no significant changes in stomatal density or size were observed. Both geo-material treatments altered leaf surface properties, particularly peltate trichome characteristics. Notably, ammonium-enriched zeolite application enhanced photosynthetic rate during early olive development, likely due to its nutritional role, and contributed to increased fruit size and oil yield. These findings highlight the potential of geo-material-based foliar treatments as an effective strategy to optimize plant physiological performance and improve olive oil production in sustainable agricultural systems. Full article

Partial nitrification-Anammox (PN-A) is a cost-effective, environmentally friendly, and efficient method for removing ammonia (NH₄⁺-N) pollutants from water. However, the limited accumulation of nitrite (NO₂⁻-N) represents a bottleneck in the development of PN-A processes. To address this issue, this study developed a composite carrier loaded with nano zero-valent iron (nZVI) and zeolite to enhance NO₂⁻-N accumulation during short-cut nitrification. The modified composite carrier revealed electropositive, hydrophilicity, and surface roughness. These surface characteristics correlate positively with the carrier’s total biomass adsorption capacity; the initial adsorption of microorganisms by the composite carrier was increased by 8.7 times. Zeolite endows the carrier with an NH₄⁺-N adsorption capacity of 4.50 mg/g carrier. The entropy-driven ammonia adsorption process creates an ammonia-rich microenvironment on the surface of the carrier, providing effective inhibition of nitrite-oxidizing bacteria (NOB). In tests conducted with a moving bed biofilm reactor and a sequencing batch reactor, the composite carrier achieved a 95% NH₄⁺-N removal efficiency, a NO₂⁻-N accumulation efficiency of 78%, and a doubling in total nitrogen removal efficiency. This composite carrier enhances NO₂⁻-N accumulation by preventing biomass washout, inhibiting NOB, and enriching PN-A functional bacteria, suggesting its potential for large-scale, stable PN-A applications. Full article

Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir to maintain an active metallic state, thereby preventing a decrease in catalytic activity in the CO-SCR reaction. Moreover, the Ba modification increased the NO adsorption of the catalyst, further improving the catalytic activity. Owing to the better anti-oxidation ability of Ir⁰ in IrBa0.2/ZSM-5(27) than in Ir/ZSM-5(27), IrBa0.2/ZSM-5(27) showed better stability than Ir/ZSM-5(27). Considering that all samples in the present study were tested to simulate actual flue gases (such as sintering flue gas and coke oven flue gas), NH₃ was introduced into the reaction system to serve as an extra reductant for NO_x. The NO_x conversion to N₂ (77.1%) was substantially improved using the NH₃-CO-SCR system. The proposed catalysts and reaction systems are promising alternatives for treating flue gas, which contains considerable amounts of NO_x and CO in oxygen-enriched environments. Full article

Volcanic tuffs rich in chabazite zeolites have been extensively examined for their potential to enhance soil properties and increase fertilizer efficiency, both in their natural state and when enriched with nitrogen (N). However, there is a scarcity of data regarding their utilization in acidic sandy soil, particularly when used alongside organic fertilizers. This paper presents the findings of a 50-day laboratory incubation study that investigated the dynamics of N pools in an acidic sandy-loam agricultural soil treated with various N sources. These sources included urea, N-enriched chabazite zeolite tuff, and pelleted composted manure applied at a rate of 170 kg N/ha. Additionally, the N sources were tested in combination with chabazite zeolite tuff mixed into the soil to assess its role as a soil conditioner. The results revealed distinct behaviours among the tested N sources, primarily impacting soil pH and N dynamics. Soil fertilized with manure exhibited slow N mineralization, whereas N-enriched zeolite displayed a more balanced behaviour concerning net NO₃⁻-N production and NH₄⁺-N consumption. Both N-enriched zeolite and urea temporarily altered the soil pH, resembling a “liming” effect, while pelleted manure facilitated a prolonged shift towards neutral pH values. Considering the water adsorption capacity of zeolite minerals, caution is advised when adjusting water content and employing combustion methods to measure soil organic matter in zeolite-treated soil to avoid potential inaccuracies. In summary, N-enriched chabazite zeolite tuff emerged as a valuable N source in acidic sandy-loam soil, offering a promising alternative to synthetic fertilizers and showcasing a sustainable means of N recycling. Full article

Resource recovery from wastewater is very important in view of a circular economy approach in the water field. Among the different technologies applied to realize circular economy, an attractive option is the use of nutrient-enriched media that can be utilized as slow-release fertilizers. Zeolites have been re-discovered for their key role in ammonium (NH₄⁺) adsorption from treated wastewater. Although many studies have been carried out to assess the ability of zeolites to adsorb NH₄⁺, only few papers concerning NH₄⁺ desorption from zeolites are available in the literature. Therefore, this study investigated NH₄⁺ desorption from mineralogically different zeolites, before (ZNS and ZNC) and after (ZSS and ZSC) their treatment with sodium chloride. The zeolites differed in mordenite content. The amount of the desorbed NH₄⁺ varied from 78 to 84% of the total NH₄⁺ adsorbed. In particular, the NaCl-treated materials showed the largest desorption (27.6 ± 0.2 mg L⁻¹, and 27.9 ± 0.7 mg L⁻¹, ZSS, and ZSC, respectively) as compared to the untreated zeolites (22.9 ± 0.3 mg L⁻¹, and 24.2 ± 0.3 mg L⁻¹, ZNS, and ZNC, respectively) because of the different affinity of the cations for the zeolite surface. A monomodal pseudo-first-order model best approximated the desorption kinetics, suggesting only one mechanism of NH₄⁺ desorption from zeolites. Such a mechanism is based on the ion exchange between dissolved Na⁺ and adsorbed NH₄⁺. The desorption kinetics also showed that NH₄⁺ desorbed slower from the NaCl-treated zeolites than the untreated ones. This effect was explained by the different affinity of Na⁺ and NH₄⁺ for the zeolite surfaces as due to the diverse sizes of the Na⁺ and NH₄⁺ hydration spheres. By revealing the effect of zeolite mineralogy and surface treatments in the desorption of NH₄⁺, this study can suggest new and effective synthetic strategies for the achievement of cheap new materials to be applied in environmental remediation within a circular economy perspective. Full article

A core–shell-derived structural magnetic zeolite imidazolate framework-67 (Fe₃O₄-COOH@ZIF-67) nanocomposite was fabricated through a single-step coating of zeolite imidazolate framework-67 on glutaric anhydride-functionalized Fe₃O₄ nanosphere for the magnetic solid-phase extraction (MSPE) of theophylline (TP). The Fe₃O₄-COOH@ZIF-67 nanocomposite was characterized through scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, Zeta potential analysis, X-ray diffraction, Brunauer–Emmett–Teller, and vibrating sample magnetometer. The material has a high specific surface area and good magnetism, which maintains the regular dodecahedron structure of ZIF-67 without being destroyed by the addition of Fe₃O₄-COOH nanospheres. The Fe₃O₄-COOH@ZIF-67 can rapidly adsorb TP mainly through the strong coordination interaction between undercoordinated Co²⁺ on ZIF-67 and –NH from imidazole of TP. The adsorption and desorption conditions, such as the amount of adsorbent, adsorption time, pH value, and elution solvent, were optimized. The kinetics of TP adsorption on Fe₃O₄-COOH@ZIF-67 was found to follow pseudo-second-order kinetics. The Langmuir model fits the adsorption data well and the maximum adsorption capacity is 1764 mg/g. Finally, the developed MSPE-HPLC method was applied in the enrichment and analysis of TP in four tea samples and rabbit plasma. TP was not detected in oolong tea and rabbit plasma, and its contents in jasmine tea, black tea, and green tea are 5.80, 4.31, and 1.53 μg/g, respectively. The recoveries of spiked samples are between 74.41% and 86.07% with RSD in the range of 0.81–3.83%. The adsorption performance of Fe₃O₄-COOH@ZIF-67 nanocomposite was nearly unchanged after being stored at room temperature for at least 80 days and two consecutive adsorption–desorption cycles. The results demonstrate that Fe₃O₄-COOH@ZIF-67 nanocomposite is a promising magnetic adsorbent for the preconcentration of TP in complex samples. Full article

Natural zeolite, as an abundant aluminosilicate mineral with a hierarchically porous structure, has a strong affinity to ammonium in solutions. Adsorption mechanism of high-concentration ammonium (1000~4000 mg-N/L) in an aqueous solution without pH adjustment onto Chinese natural zeolite with the dosage of 5 g/L was revealed by the strategy of experimental optimization integrated with Molecular Dynamics (MD) simulation, and found the maximum ammonium adsorption capacity was 26.94 mg/g. The adsorption kinetics and isotherm analysis showed that this adsorption process fitted better with descriptions of the pseudo-second-order kinetics and Freundlich model. The theoretical calculations and infrared-spectrum characterization results verified the existence of hydrogen bonds and chemisorption. Therefore, the adsorption mechanism by natural zeolites of high-concentration NH₄⁺ is defined as a process under the joint influence of multiple effects, which is mainly promoted by the synergy of the ion exchange process, electrostatic attraction, and chemisorption. Meanwhile, the hydrogen bond also plays an auxiliary role in this efficient adsorption. This study presents important theoretical significance for enriching the mechanism of zeolites adsorbing NH₄⁺ from water, and provides reference and theoretical guidance for further exploring the potential application of natural zeolites. Full article

Eutrophication is an emerging worldwide issue concerning the excessive accumulation of various pollutants in sediments, owing to the release of industrial or household wastewaters to coastal areas. The coastal sediment of Goseong Bay in the Republic of Korea is organically enriched with pollutants, including heavy metals, sulfide, phosphate, and ammonia. Microbial remediation and capping techniques have been suggested as effective routes for sediment remediation. In this study, Bacillus subtilis zeolite (BZ) was used as a sediment capping material, and effective remediation of coastal sediment was observed in a 40-day laboratory microcosm experiment. A significant decrease in the sediment water content and reduced concentration of acid volatile sulfide were observed in the BZ-capped sediment. In the overlying water and pore water, significant decreases in phosphate and dissolved inorganic nitrogen (DIN; NO₂-N + NO₃-N and NH₄-N) concentrations were observed in the BZ-treated experiment. Based on our findings, we conclude that BZ could be an effective capping material for coastal sediment remediation. Full article

Using zeolite-rich tuffs for improving soil properties and crop N-use efficiency is becoming popular. However, the mechanistic understanding of their influence on soil N-processes is still poor. This paper aims to shed new light on how natural and NH₄⁺-enriched chabazite zeolites alter short-term N-ammonification and nitrification rates with and without the use of nitrification inhibitor (DMPP). We employed the ¹⁵N pool dilution technique to determine short-term gross rates of ammonification and nitrification in a silty-clay soil amended with two typologies of chabazite-rich tuff: (1) at natural state and (2) enriched with NH₄⁺-N from an animal slurry. Archaeal and bacterial amoA, nirS and nosZ genes, N₂O-N and CO₂-C emissions were also evaluated. The results showed modest short-term effects of chabazite at natural state only on nitrate production rates, which was slightly delayed compared to the unamended soil. On the other hand, the addition of NH₄⁺-enriched chabazite stimulated NH₄⁺-N production, N₂O-N emissions, but reduced NO₃⁻-N production and abundance of nirS-nosZ genes. DMPP efficiency in reducing nitrification rates was dependent on N addition but not affected by the two typologies of zeolites tested. The outcomes of this study indicated the good compatibility of both natural and NH₄⁺-enriched chabazite zeolite with DMPP. In particular, the application of NH₄⁺-enriched zeolites with DMPP is recommended to mitigate short-term N losses. Full article

The use of rocks containing high amounts of natural zeolites (zeolitites) as soil amendment has been found as a valuable method for increasing agriculture sustainability. However, the potentialities and the effects of zeolitites on the biogeochemical cycles of nitrogen (N) and carbon (C) have still not been clearly addressed in the literature. The objective of this study was therefore to investigate the N and C pools and ¹⁵N distribution in an agricultural soil amended with both natural and NH₄⁺-enriched zeolitites with the aim of understanding their effects on the soil-plant system, during sorghum cultivation, under fertilization reductions. Zeolitites were applied to an agricultural soil both at natural state (5 and 15 kg m⁻²) and in an enriched state with NH₄⁺ ions from pig slurry (7 kg m⁻²). Both zeolitites at natural and enriched state increased soil cation exchange capacity and affected microbial biomass, causing an initial decrease of microbial C and N and then a possible increase of fungal population. N-NO₃⁻ content was lower in natural zeolitite treatments, that lead to a lower NO₃⁻ availability for denitrifying bacteria. Zeolitites slightly affected the fixed N-NH₄⁺ pool. δ¹⁵N turnover indicated that N from NH₄⁺-enriched zeolitites remained in the soil until the growing season and that fertilizers partially substituted the fixed pool. Leaf δ¹⁵N content indicated that plants assimilated N from NH₄⁺-enriched zeolitites and evidenced a higher fertilization recovery in natural zeolitite treatments. Organic C tended to be higher in all zeolitite treatment rhizospheres. In soils amended with zeolitites at natural state (at both application rates) sorghum yield was similar (+3.7%) to that obtained in the control while it was higher (+13.9%) in the plot amended with NH₄⁺-enriched zeolitites. Full article