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Article

Modified Compositions of Micelle–Clay and Liposome–Clay Composites for Optimal Removal from Water of Bacteria and Hydrophobic Neutral Chemicals

by
Ana R. Benitez
1,
Dani Margalit
1,
Marklen Ryskin
1,
Maoz Dor
1,
Uri Shuali
1,
Shlomo Nir
1,*,
Tamara Polubesova
1,
Julius Ben-Ari
1,
Jeny Kertsnus-Banchik
1 and
Tomas Undabeytia
2
1
Soil and Water Department, The R.H. Smith Faculty of Agriculture, Food and Environment, University of Jerusalem, Rehovot 76100, Israel
2
Instituto de Recursos Naturales y Agrobiologia, IRNAS-CSIC, Reina Mercedes 10, 41012 Sevilla, Spain
*
Author to whom correspondence should be addressed.
Appl. Sci. 2022, 12(6), 3044; https://doi.org/10.3390/app12063044
Submission received: 15 February 2022 / Revised: 9 March 2022 / Accepted: 11 March 2022 / Published: 16 March 2022
(This article belongs to the Section Environmental Sciences)
Browse Figures
Versions Notes

Abstract

:
The efficiency in water treatment by granulated complexes formed from the clay bentonite with (i) micelles of the cations of octadecyltrimethyl-ammonium (ODTMA) or (ii) liposomes of didodecyldimethyl-ammonium (DDAB) was investigated. The bentonite–ODTMA complexes were synthesized in three variations: I. mass ratio of 68/32, which resulted in an excess of positive charge of half of the clay cation exchange capacity and is denoted “ordinary”; II. complexes having higher loads of ODTMA, denoted “enriched”; and III. “neutral”. These variations were designed to optimize the efficiency and reduce the costs of water treatment. “Ordinary” and “neutral” complexes of DDAB were also synthesized. The “ordinary” complex of ODTMA was shown to be efficient in the removal of anionic/hydrophobic molecules and bacteria. The “enriched” complexes were more active in removal of bacteria from water by filtration due to the higher release of free ODTMA cations, which causes biostatic/biocidal effects. The corresponding “ordinary” and “neutral” complexes of ODTMA and DDAB yielded the same efficiency in removal from water of the neutral and hydrophobic herbicides, S-metolachlor (i) and alachlor (ii), respectively. Model calculations, which considered sorption/desorption and convection yielded simulations and predictions of filtration results of the herbicides. The neutral complexes are advantageous since their production saves about 1/3 of the amount of ODTMA or DDAB, which constitutes the expensive component in the respective composite.

1. Introduction

The micelle–clay complex was originally designed by Mishael et al. [1] for optimizing slow-release formulations of anionic herbicides, such as sulfometuron. The complex is synthesized by interacting clays or clay–minerals with organic cations whose critical micelle concentration (CMC) is small. A small value of the CMC of the chosen organic cation enables a fraction of the solution of cations residing originally in micelles to be enhanced. It should be emphasized that complexes formed by addition of the cations as monomers were not efficient in adsorbing the anionic herbicides.
Two quaternary amine cations (QACs) were chosen: ODTMA and Benzyldimethylhexadecylammonium (BDMHDA) whose alkyl chains include 18 and 16 carbon atoms, and their CMC values are 0.3 mM and 0.6 mM, respectively. An optimal loading of the organic cations by montmorillonite was 120 cmol/kg of clay-mineral, which amounts to a net positive charge of the complex of one half of the cation exchange capacity (CEC) of the clay–mineral. In the case of a clay, such as bentonite, the preferred amount of net positive charge was also one half of the CEC [1]. The other characteristics of the micelle–clay are large surface area per weight and existence of hydrophobic domains. Polubesova et al. [2] demonstrated that such micelle–clay complexes can be employed in removal of pollutants from water by filtration. Some examples are removal of hydrophobic and/or anionic herbicides [3,4] and removal of pharmaceuticals [5,6,7,8,9,10,11]. Since 2012 most of the experiments employed the complex exclusively in a granulated form, which can enable flow in the filter at acceptable flow velocities for upscaled projects.

Role of Released Cations during Filtration

The Israeli Health ministry issued a conditional permission to apply the micelle–clay technology for treatment of drinking water and unrestricted irrigation, provided that the concentration of the released cation, e.g., ODTMA, would not exceed 100 µg/L. The concentrations of released ODTMA during filtration of 100 m3 of water by a pilot filter filled with granulated complex ODTMA–clay were between 25 and 50 µg/L [12]. Using a small column (1.6 cm × 20 cm) filled with granulated complexes followed by a similar one filled with activated carbon indicated that after passing 64 L, the concentrations of released ODTMA and BDMHDA cations were 82 and 1817 µg/L, respectively; whereas, after passing through the second (GAC) filter, the corresponding values were reduced to 1.6 and 0.9 µg/L [13]. Significantly more release of BDMHDA than ODTMA has been found earlier for the powdered complexes [14].
Kalfa et al. [13] pointed out that the BDMHDA–clay complex had an advantage over the complex based on ODTMA in reducing the number of emerging bacteria, despite similar numbers of bacteria retained by the filters, which included fresh or regenerated complexes. Designed experiments supported a hypothesis that the advantage of BDMHDA–clay over ODTMA–clay complexes in removal of bacteria from water was due to larger concentrations of released BDMHDA than ODTMA cations during filtration. It was suggested that the relatively larger numbers of released BDMHDA cations exert a much larger biocidal or biostatic effect on the emerging bacteria than in the case of ODTMA. This effect was seen both with E-coli or total bacteria count (TBC). For the purpose of water purification, the biostatic effect by free monomers is sufficient. Sukenik et al. [15] demonstrated that small concentrations of free ODTMA cations abolished the photosynthetic activities of two cyanobacteria, Microcystis aeruginosa and Aphanizomenon ovalisporum, which amounted to cell killing.
The main aim of the current study is to test variations in composite composition to enhance the capacity for removal of (1) bacteria and (2) neutral hydrophobic pollutants.
  • An increase in concentration of released cations, which is expected for composites formed with a larger added amount of cation per clay than in the ordinary one [12,14], will result in a larger biocidal/biostatic effect and enable the micelle–clay complex to remove more TBC from water by filtration. The tests will involve a synthesis of a granulated complex obtained by adding the salt of ODTMA at a larger ratio to bentonite than in the ordinary complex during preparation of the complex.
  • In the case of optimization of removal of neutral hydrophobic pollutants. the tested modification will deal with both the micelle–clay and liposome–clay [12,14,16] composites. Liposome–clay complexes are similar to the micelle–clay ones but are prepared by adsorption on the clay of vesicles whose alkyl ammonium surfactants have two long alkyl chains. In this case, the concentrations of monomers in solution are significantly smaller (Undabeytia et al.) [17] than those of micelle-forming surfactants with one long alkyl chain of the same length. As an example, the surfactant didodecyldimethylammonium bromide (DDAB) remains in solution as monomers up to 35 µM [18], whereas the CMC of dodecyltrimehylammonium bromide is 3.49 mM [19].
Removal of neutral hydrophobic molecules from water by a composite micelle (ODTMA)–clay, or liposome (DDAB)–clay is not expected to increase by loading the cation beyond neutrality of the clay. If this is confirmed, then, for removal of neutral hydrophobic pollutants from water, the synthesis of clay composites can be accomplished with one third less of the amount of the organic cation, which is the expensive component. The tests by filtration, will compare the efficiency of pollutant removal by an ordinary (positively charged) vs. neutral clay composite.

2. Materials and Methods

2.1. Materials

Bentonite was purchased from Tolsa-Steetley, Retford, U.K. Alachlor, DDAB and the organic cation, ODTMA, formulated as a bromide salt were obtained from Sigma-Aldrich (Sigma Chemical Co., St. Louis, MO, USA). A non-woven polypropylene geo textile filter was obtained from Markham Culverts Ltd., Lae, Papua-New Guinea. The analytical standard of S-metolachlor with a purity of 98.6% was obtained from Dima Technology Inc. (Foothill Ranch, CA, USA). Acetonitrile and water, high-performance liquid chromatography (HPLC) grade, were purchased from Merck (Darmstadt, Germany).

2.2. Methods

2.2.1. Preparation of Granulated Complexes

Granulated micelle–clay complexes of ODTMA of a diameter size between 0.3 and 2 mm were prepared as described by Nir et al. [12], and Nir and Ryskin [20]. The granules included 3% of water. The ordinary complex was synthesized from 32 g of ODTMABr salt and 68 g of Na-bentonite per L. New complexes were synthesized from different ratios between the salt and the clay: (i) enriched complexes at ratios of 36/64 (“20%”) and 35/65 (“14%”); (ii) neutral complex at a ratio of 24/76. In the preparation of clay–DDAB granules the surfactant/clay ratios were 20.8/50 (42%) and 20/75 (27%) for loading of the surfactant beyond the CEC (33% excess) and neutral, respectively.
Documentation is given for the concentrations of the three main anions, Br−, SO4−2, and Cl− in the water emerging from the filter press during the granulation of the micelle–clay complexes. These results and their expected values are given and discussed in the Supplementary material.

2.2.2. Filtration Procedure

Filtration experiments were carried out using granulated composites packed in filter columns. Geotextile was used as covers at the inlet and outlet of each column. The active layer in the columns was a length of 20 cm and a diameter of 6.5 or 1.6 cm. The larger columns were operated at a flow rate of 1 L/min, whereas the small columns were operated at flow rates between 4 and 7 mL/min. The columns were connected to a peristaltic pump (Cole-Palmer Masterflex L/S) with silicon tubes in two sets as a duplicate. In the case of small filters, the silicone tubes used were disinfected prior to use by 275 mL of a 0.05 M HCl solution at a constant flow rate followed by washing with tap water. Columns were saturated with tap water from the outlet at a flow rate of 2 to 5 mL/min moving upward to eliminate air pockets and channeling. In the case of clay–DDAB granules, filtration proceeded only with the hydrophobic herbicide, alachlor; the columns of 2 cm in diameter were packed with 15 g of clay–DDAB granules, yielding a height of bed of 5.5 cm. The pore volume was 13 mL, and the flow rate used was 3.5 mL/min.
The adsorption and convection phenomena occurring in the filter were analyzed by the model described by Nir et al. [3]. A column of length L is filled with material whose initial molar concentration of adsorbing sites is Ro, whose concentration changes later to R(X,t). The beginning and end of the filter are at the coordinates X = 0 and X = L, respectively. The pollutant concentration at the inlet, Co, is constant, i.e., C(X,t) = Co, for X ≤ 0, where t denotes time. The kinetic parameters are C1 (M−1 min−1, rate constant of forward adsorption), D1 (min−1, rate constant of desorption), and v (flow velocity).
dC(X,t)/dt = −v𝜕C/𝜕X − C1∙C(X, t)∙R(X, t) + D1∙(Ro − R(X, t))
The statistical criteria employed for simulation and prediction of certain experimental results of filtration by the calculations were the values of R2 and RMSE.

2.2.3. Analysis of TBC

Tap water and filtration outlet water from each column were collected in 500 mL bottles. TBC concentrations were determined by an external certified laboratory (Aminolab, Ness Ziona, 70400, Israel) in accordance with standard methods [21].

2.2.4. Regeneration

Regeneration of used granules was performed by applying a microwave (MW) as described by Kaya et. al. [22]. Briefly, the micelle–clay samples were placed into a small MW compatible bowl and weighed. The microwave was operated at 700 W by pulse durations to prevent overheating. The pulse durations were 1 min, 30 s, or 20 s, depending on the remaining water content as determined by the weight of the sample until the original weight of 32 g was approached.

2.2.5. Analysis of Non-Ionic Herbicides

Metolachlor concentrations used in filtration experiments packed with ODTMA–clay granules were 50 and 10 mg/L, and eluates from column filters were collected during 18 and 24 h of filtration and analyzed by HPLC (Agilent 1200, obtained from Agilent, Santa Clara, CA, USA) equipped with a diode-array detector as described [23]. Prior to HPLC analysis, the samples were filtered with acrodisc (polypropylene) filters (Beith Dekel, Ra’anana, Israel) of 0.45 µm pore diameter. Filtration experiments with DDAB–clay granules used alachlor whose initial concentrations were 50 mg/L. The HPLC column was a reverse-phase C-18 column (5 µm particle size, DM (mm) 150 × 4.6) operated at a flow rate of 1.0 mL min−1. The measurements were isocratic. The mobile phases were binary mixtures of acetonitrile and water at (v/v) ratios of 80:20 for metolachlor and 60:40 for alachlor. The wavelengths were 225 nm for metolachlor and 240 nm for alachlor.

3. Results

3.1. Removal of TBC from Drinking Water by Filtration

This subsection deals with testing the possibility to enhance the capacity of micelle–clay granulated complexes in purification of drinking water from TBC by increasing the loading of the organic cation, ODTMA, during preparation of the complex.

3.1.1. Filtration at a Flow Rate of 1 L/min (Flow Velocity 18 m/h; Retention Time 0.67 min)

In Table 1 and Table 2, the efficiency of removal of TBC by the ordinary complex was compared with that of an enriched complex in which the amounts of ODTMA added during the preparation of the granulated complex (enriched) were increased. Two columns (D = 6.5 cm ● L = 20 cm) exclusively containing granules of each type were fed with water from a container filled continuously with tap water. The filtration flow rate for 3 h per day was 1 L/min, which corresponds to a flow velocity of 18 m/h. This flow regime is quite demanding for a domestic filter, where a flow of several liters is usually followed by a period of rest, and the total amount filtered rarely exceeds 30 L per day. Samples were taken in the morning and afternoon except on the first day in each case. In the morning, the first filtered volume of 0.25 L was spilled, and then a sample of 1 L was taken; after that, the flow proceeded for 3 h, and another sample was taken. This procedure was in accordance with certain tests on domestic filters in Israel. A criterion was set that the number of bacteria in the filtered water should not exceed 1000/mL for an acceptable quality of drinking water. The first experiment (Table 1) started on 19 February when the reproduction rate of bacteria in water is relatively minimal, whereas in Table 2, the starting day was on 3 June, towards the end of spring season. The total filtered volumes were 1630 L and 1270 L, in Table 1 and Table 2, respectively.
Sampling columns 1 and 2 in Table 1 indicated that filters filled with the enriched complex yielded in all cases a small number of emerging bacteria, whereas in the case of the filters filled with the ordinary complex, four samples exceeded the criterion of 1000 TBC/mL from one of the columns. Larger observed numbers were sampled in the morning, i.e., 20 h or 47 h after a halt of the flow.
The results in Table 2 (June) indicate that the water fed into the filters included in 7 out of 10 cases very large numbers of TBC, which were significantly reduced by filtration. For instance, for an initial value of 62,000/mL at the entry points to the filters, the number of emerging TBC/mL was reduced to less than 100 on the average. The observed numbers of samples which indicated more emerging TBC/mL than 1000 were 4 and 11 in the cases of the enriched and ordinary complexes, respectively. Clearly, the enriched complex was superior to the ordinary one in its efficiency of removal of bacteria from drinking water.

3.1.2. Removal of TBC from Drinking Water at a Flow Rate of 6 mL/min

Six filter columns containing 32 g of granulated ODTMA–clay were operated simultaneously. Two types of micelle–clay granules were used: (1) ordinary complex, and (2) granules in which the amount of ODTMA added during the preparation of the granulated complex was increased by 15%. Before the start of this experiment, both types of granules were dried in a MW oven to remove possible extra humidity that might have accumulated during storage. Each sample was dried individually for 10 periods of 20 s, but the mass loss per sample of 40 g amounted to 0.18 g on average. The number of emerging TBC per mL after given volumes of continuous filtration by using fresh granules is given in Table 3. The average volume filtered per day was 8.64 L.
Inspection of columns 2 and 3 of Table 3 indicates that the numbers of samples with 1000 or more TBC/mL were 3 and 1 in the case of ordinary (R) and enriched (E) columns, respectively. Hence, in accordance with Table 1 and Table 2, the enriched complex yielded better results in filtration of bacteria.
The average capacity of the column filters can be defined by dividing the number of liters of water passed with less than 1000 CFU per mL by the mass in grams of granulated material included in a column. For the enriched complex, the results in Table 3 gave a capacity of: (43.2 · 2/3 + 34.6) L/32 g = 2 L/g.

3.1.3. Results of First Regeneration

The micelle–clay granules from each column filter were subjected to MW radiation as in [22]. The sample mass was measured after each heating-drying period. The used granules from each column were first exposed to 30 s of heating, and when their weight exceeded by 5% the original weight of fresh granules, the samples were heated in repetitions of 20 s. Table 4 indicates the results of filtration by the column filters after the first regeneration.
Retention time and flow rate were as in Table 3.
Within statistical uncertainty, the results in Table 4 do not show an advantage of any of the reused complexes in removal of bacteria from drinking water. The results in the last column in Table 3 were retained for completeness and for demonstrating that the regeneration reduced on average the number of emerging bacteria 800-fold. The capacity in this experiment was calculated as in the case of Table 3 by (25.9 + 25.9·2/3 + 25.9/3) L/32 g = 1.7 L/g, which is 85% of the capacity of the enriched complex, similarly to previous outcomes by Rakovitsky et al. [24] and Kalfa et al. [13].

3.2. Tests of the Efficiency of the Ordinary vs. Neutral Complex in Removal from Water of the Non-Ionic Herbicide Metolachlor

Metolachlor concentrations in drinking water are not allowed above 0.1 µg/L in Europe. A metolachlor solution was filtered by two types of complexes: ordinary (loading of ODTMA is 50% above the CEC of the clay), and neutral. Two solutions of metolachlor were filtered, 50 mg/L (Figure 1) and 10 mg/L (Figure 2), and the results were modeled as in [3].
The fractions of metolachlor sorbed by passing a solution of 50 mg/L were 71% and 74% in the cases of the ordinary and neutral complexes, respectively. The passage of a five-fold or less concentrated solution yielded somewhat larger percentages of metolachlor sorption (76% and 80%), whereas the adsorbed amounts were about 24% less in the case of the more dilute solution during 48 h, in comparison with 17 h in the case of the more concentrated solution.
The results of metolachlor filtration (50 mg/L; Figure 1) by the neutral complex were fitted to the experimental values by using the values of 3 parameters: R0 = 0.042 M, the molar concentration of adsorbing sites in the filter; C1 = 30 M−1 min−1, the forward rate constant of sorption; D1 = 0.0004 min−1, the rate constant of desorption. The same values of the parameters yielded reasonably well predictions of the experimental results of percent adsorbed in Figure 2.
The values obtained for the statistical criteria of the fits were R2 = 0.97 and 0.944 and RMSE of 1.8 and 2.1 for the filtration of the 50 mg/L and 10 mg/L solutions, respectively.
The main outcome of the results is that the capacity of the neutral complex to remove metolachlor from water is not less than that of the ordinary complex, despite using 1/3 less of the cation ODTMA, which is the more expensive component in the granular complex.
Percent of S-metolachlor adsorbed by: (exp.) Applsci 12 03044 i001 ordinary complex; (exp.) Applsci 12 03044 i002 neutral complex; Applsci 12 03044 i003 calculated for neutral complex. The calculations according to [3] employed the following values of the parameters: R0 = 0.042 M; C1 = 30 M−1 min−1; D1 = 0.0004 min−1. The relative experimental errors in percent adsorbed were less than 10% during the first 10 h of filtration, about 20% at 11–14 h, and about 30% at a later time.
Percent of S-metolachlor adsorbed by: (exp.) Applsci 12 03044 i001 ordinary complex; (exp.) Applsci 12 03044 i002 neutral complex; Applsci 12 03044 i003 calculated percent adsorbed by neutral complex. The calculations employed the same values of parameters as in Figure 1. The relative experimental errors in percent adsorbed were less than 5% during the first 24 h of filtration, and about 5 to 20% later.
The results of filtration of alachlor (50 mg/L) by the DDAB–clay composite are shown in Figure 3, which also gives the calculated values to the filtration of metolachlor by the micelle–clay composite; there was no difference, similarly in the elution from columns prepared with both complexes, neutral and charged, and the model could yield good simulations of the filtration results.
The values of the kinetic parameters are given in Table 5. The values of R0 are 0.042 and 0.15 M for the micelle–clay and liposome–clay, whereas the values of the affinity coefficient K = C1/D1 of these composites are 7.5∙104 and 1.8∙104 M−1, respectively. It is well known that if the value of R0 during the fitting of results by the Langmuir equation is too large, then the fits will yield a small value of K and vice versa. In fact, the values of the fractions adsorbed are largely dictated by the products R0∙K, which are 3150 and 2700 for the micelle–clay and liposome–clay composites, respectively. These values which are just 20% larger for the micelle–clay case are similar for both composites. It is of interest to note that the filter lengths and flow velocities were 20 cm and 3 cm/min for the micelle–clay, whereas for the liposome–clay the corresponding values were 5.5 cm and 1.1 cm/min. It is well known [3] that elongation of a filter by a factor X yields the same results at a X-fold larger flow velocity, but using the same velocity as before would yield a larger capacity. When these differences are taken into account, it follows that the products R0∙K are practically identical for both composites.

4. Discussion

4.1. Filtration of Total Count Bacteria

Removal of bacteria from water was demonstrated by filtration based on adsorption of the bacteria by micelle–clay complexes [12,13,15,25,26,27,28] and by polymer–clay composites [29,30]. In parallel, biostatic and/or biocidal effects on bacteria by several quaternary amine cations were demonstrated [19,31]. The mechanistic suggestion that the release of an organic cation, such as ODTMA, during filtration can enhance the capacity of the filter in removal of bacteria from water was emphasized in [13,15,32,33,34]. The results in [12,13,14] contributed to the notion that the release of ODTMA cations during filtration from an enriched granulated complex would exceed the release from an ordinary complex. The results in Table 1, Table 2 and Table 3 demonstrate that granulated micelle–clay complexes with larger ratios of ODTMA cations to the clay were more efficient in removal of total count bacteria from drinking water, in line with the hypothesis put forward in the Introduction section.
It is of interest to examine in some detail the excessive numbers of bacteria reported in Table 1 in the samples taken in the morning, compared with those after 3 h of filtration. It is noted that water pores comprise about 45% of the volume of a filter, which contains granulated ODTMA–bentonite in addition to a certain water layer at the upper hand of the filter. In the initial stages of filtration in the current experiments (after 2 days, Table 1, Wednesday), only a few bacteria were found emerging through all the filters, but eventually, the pores in the filters included free bacteria, which could reproduce during halted filtration for 20 h on Wednesday afternoon or for 67 h from Thursday afternoon until Sunday morning. The numbers of bacteria emerging through the filters were larger in the respective samples taken from one of the columns filled with the ordinary complex. On Sunday afternoon the numbers of TBC emerging were small again. However, the numbers of bacteria emerging from the filters with enriched complex remained small during the whole experiment due to the larger numbers of released ODTMA cations, which exerted biocidal/biostatic effects.
The results in Table 1 indicate that the volume which could be filtered with emerging bacteria below 1000 TBC/mL through a column including the enriched complex was larger than 1630 L since the samples taken in the morning and afternoon of the last day gave small average numbers of emerging bacteria, 35 and 0 per mL, respectively. The capacity deduced for the enriched granular complex (Table 1) is larger than 1630 L/550 g, which yields 3 L/g, in comparison with 2 L/g deduced from the results in Table 3. It is remarkable that the flow velocity was 10-fold larger in the experiment represented by Table 1 than that reported in Table 3. Previous experiments on removal of chemicals from drinking water in [12] or E. coli [13]; and TBC in [22] as well as model calculations [12,13,33] indicate that it might be expected that the observed capacity in Table 1 would be several-fold smaller than in the case of Table 3. This is an interesting issue, which may need more studies. At this stage it may be speculated that it is possible that collisions encountered by bacteria moving at a high velocity through the narrow metal exit can result in partial inactivation of the bacteria. In the case of the enriched complex, which releases more ODTMA cations during filtration, apparently more bacteria were inactivated. To the best of our knowledge, this possibility has not been mentioned in scientific publications. Quite a few publications indicated that enhanced flow velocities in pipes or open channels resulted in a decrease in biofilm accumulation [35,36]. However, in these cases the decrease in biofilm mass was explained by increase in flow shear stress.

4.2. On the Choice of Optimal Composites for Removal from Water of Neutral Hydrophobic Molecules

Figure 1, Figure 2 and Figure 3 demonstrate that the removal from water of Metolachlor by micelle–clay and Alachlor by liposome–clay composites yields similar outcomes by the ordinary and neutral composites in both cases, which gives an illustration for economical preference in using the neutral complex since its use enables for the saving of a third of the expensive part of the granular composites. However, different patterns can be exhibited for an optimal removal from water of other neutral and hydrophobic molecules. This study demonstrates a simple test by filtration on a small scale, which will enable to choose between clay composites before upscaling.

5. Conclusions

Three patterns are presented for optimal water purification by granulated micelle (ODTMA)– and liposome (DDAB)–clay composites. The ordinary complex, which has charge reversal of 50%, or 12.5% of the CEC of the clay in the micelle–, or liposome–clay, respectively, is efficient in removal from water of microorganisms and chemicals, which are hydrophobic and anionic The neutral and ordinary complexes of the micelle– or liposome–clay yielded similar removal of the neutral and hydrophobic herbicides, metolachlor and alachlor, respectively, which implies reduced amounts of the expensive component in the neutral composites.
The enriched complex, which was synthesized by adding a few percent excess of ODTMA above the amount used in the preparation of the ordinary one, reduced significantly the concentrations of emerging TBC during filtration, in particular, after a halt in filtration for one or more days.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/app12063044/s1, Table S1. Concentrations of main anions in water during granulation of the complex. Supplementary S2. title Results and discussion: concentrations of Bromide, Sulfate and Chloride in the water emerging from the filter press during granulation of ODTMA-bentonite complex.

Author Contributions

A.R.B., conceptualization, data curation (Table 3 and Table 4, Figure 1 and Figure 2), investigation; D.M., conceptualization, data curation (Table 1 and Table 2); M.R., conceptualization, data curation, (design and production of granulated complexes); M.D., conceptualization, data curation (Figure 1 and Figure 2); U.S., conceptualization, investigation; S.N., design of study, conceptualization, funding acquisition, modeling (Figure 1 and Figure 2); T.P.; conceptualization, data curation (Figure 1 and Figure 2); J.B.-A., J.K.-B., data curation, formal analysis (Table S1); T.U., conceptualization, data curation, investigation, funding acquisition, modeling (Figure 3, Table 5). All authors have read and agreed to the published version of the manuscript.

Funding

S.N. acknowledges financial support by the Ministry of Science and Technology, Israel and the Ministry of Science and Technology of the People’s Republic of China (Grant No. 3-15707). T.U. acknowledges financial support by the grant P18-RT-5098 from Junta de Andalucia supported by the European Regional Development Fund (FEDER).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is contained within the article or Supplementary material.

Conflicts of Interest

The authors declare no conflict of interest.

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Applsci 12 03044 g001 550
Figure 1. Percent adsorbed during filtration of metolachlor (50 mg/L).
Figure 1. Percent adsorbed during filtration of metolachlor (50 mg/L).
Applsci 12 03044 g001
Applsci 12 03044 g002 550
Figure 2. Percent adsorbed during filtration of metolachlor (10 mg/L).
Figure 2. Percent adsorbed during filtration of metolachlor (10 mg/L).
Applsci 12 03044 g002
Applsci 12 03044 g003 550
Figure 3. Eluted fractions of alachlor and its modeling in filtration experiments including clay–DDAB complexes.
Figure 3. Eluted fractions of alachlor and its modeling in filtration experiments including clay–DDAB complexes.
Applsci 12 03044 g003
Table
Table 1. Removal of bacteria from drinking water by filters containing an ordinary or enriched granular complex (10% increased amount of cation during preparation of complex).
Table 1. Removal of bacteria from drinking water by filters containing an ordinary or enriched granular complex (10% increased amount of cation during preparation of complex).
Total Count of Bacteria Emerging from Filters per mL
Enriched GranulesOrdinary GranulesBacteria per mL at Entry to FiltersVolume FilteredDay
1212(CFU/mL)(L)
<1<15<1<1180Mon.
281<128 Tue. M
<1<1<1<11360Tue.
<1<1<1<1<1 Wed. M
<1<1<1<1<1540Wed.
<13<13140 Thu. M
<1<1<1<1<1720Thu.
<18<11600 b370 Sun. M
<1<1<13220900Sun.
<18242,000 a630 Mon. M
<1<1<116101080Mon.
<12<1240 c210 Tue. M
<1<168 c2161260Tue.
55 c<1<188,000 a6 Wed. M
<1<1<185 c951440Wed.
37 c32 c1150,000 a120 Thu. M
<1<1<1190 c1101630Thu.
The diameter of each filter was 6.5 cm, and the length of active layer was 20 cm. Each filter contained 550 (g) of ordinary or enriched complex. Ordinary complex was prepared from 68 g of Na–bentonite clay and 32 g of ODTMABr per L; the enriched complex included 65 g of Na–bentonite clay and 35 g of ODTMABr per L. The letter M indicates that a sample of 1 L was taken in the morning after the filter(s) were not operating for 20 h or 67 h; the other samples were taken after 3 h of operation in the afternoon. Estimated relative errors were 50%, 30%, and 20% in cases a, b, and c, respectively; in other cases they were 10% or less.
Table
Table 2. Removal of bacteria from drinking water by filters containing an ordinary or enriched granular complex (15% increased amount of cation during preparation of complex).
Table 2. Removal of bacteria from drinking water by filters containing an ordinary or enriched granular complex (15% increased amount of cation during preparation of complex).
TBC Emerging from Filters per mL
Enriched GranulesOrdinary GranulesBacteria per mL at Entry to FiltersVolume FilteredDay
1212(CFU/mL)(L)
1<1<1<11180Sun.
96c32 c1200 b11<1180Mon. M
78c87 c5200 b73 c350360Tue. M
87c670 b29,000 a4800 b23,000 a540Wed. M
150b1400 b15,000 a600 b12,000720Thu. M
1415,000 a120 b11,000900Thu.
43,000 a7100 a>57,000 a6700 a15,000 Sun. M
55 c110 c95 c762,0001080Sun.
620 b610 b>57,000 a1100 b6900 Mon. M
220 b3000 b2900 b710 b15,0001270Mon.
The filters and flow rates were as in Table 1. Ordinary complex was as in Table 1. The enriched complex included 64 g of Na–bentonite clay and 36 g of ODTMA Br per L. The letter M indicates that a sample of 1 L was taken in the morning after the filters were not operating for 20 h. Estimated relative errors were 50%, 30%, and 20% in cases a, b, and c, respectively; in other cases they were 10% or less.
Table
Table 3. Removal of TBC by filtration with fresh ODTMA granules (CFU/mL).
Table 3. Removal of TBC by filtration with fresh ODTMA granules (CFU/mL).
Source of SampleVolumes Filtered (L)
43.277.8112.3138.2
Tap13111<1
Container47528<1
R11600 b253 b2300 b3400 b
R2267 c1000 b18,000 a
R37100 a2500 b3500 b20,000 a
E1475 b40 c1400 b11,000 a
E21758 c3200 b29,000 a
E31300 b169 b5300 b54,000 a
The experiment started on 17 January 2020 and was completed by 2 February 2020. Tap and container refer to continuous tap and container water inlets, respectively. R1–3 refer to columns containing an ordinary complex. E1–3 refer to columns containing an enriched complex (15% excess cation during preparation). Estimated relative errors were 50%, 30%, and 20% in cases a, b, and c, respectively; in other cases they were 10% or less. Retention time was 6.7 min.
Table
Table 4. Removal of TBC by ODTMA granules after first regeneration (CFU/L).
Table 4. Removal of TBC by ODTMA granules after first regeneration (CFU/L).
Source of SampleVolumes Filtered (L)
25.951.886.4
Tap89111
Container8251
R114600 b19,000 a
R290 c755 b15,000 a
R318435 b905 b
E1<111610 b
E24222 b3400 b
E352 c6400 a180,000 a
The experiment started on 10 February 2020 and was completed by 20 February 2020. Tap and container refer to continuous tap and container water inlets, respectively. Samples R1–3 and E1–3 denote columns, which contained ordinary and enriched complexes, respectively. Estimated relative errors were 50%, 30%, and 20% in cases a, b, and c, respectively; in other cases they were 10% or less.
Table
Table 5. Calculated parameters by the adsorption–convection model for the fit of experimental data of metolachlor and alachlor filtration by ODTMA– and DDAB–clay composites.
Table 5. Calculated parameters by the adsorption–convection model for the fit of experimental data of metolachlor and alachlor filtration by ODTMA– and DDAB–clay composites.
Metolachlor, Micelle–Clay
Ro (M)C1 (M−1 min−1)D1 (min−1)K (M−1)Ro·KR2RMSE
0.042304·10−47.5·10431500.971.8
Alachlor, liposome–clay
Ro (M)C1 (M−1 min−1)D1 (min−1)K (M−1)Ro·KR2RMSE
0.15201.1·10−31.8·10427000.980.02
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Benitez, A.R.; Margalit, D.; Ryskin, M.; Dor, M.; Shuali, U.; Nir, S.; Polubesova, T.; Ben-Ari, J.; Kertsnus-Banchik, J.; Undabeytia, T. Modified Compositions of Micelle–Clay and Liposome–Clay Composites for Optimal Removal from Water of Bacteria and Hydrophobic Neutral Chemicals. Appl. Sci. 2022, 12, 3044. https://doi.org/10.3390/app12063044

AMA Style

Benitez AR, Margalit D, Ryskin M, Dor M, Shuali U, Nir S, Polubesova T, Ben-Ari J, Kertsnus-Banchik J, Undabeytia T. Modified Compositions of Micelle–Clay and Liposome–Clay Composites for Optimal Removal from Water of Bacteria and Hydrophobic Neutral Chemicals. Applied Sciences. 2022; 12(6):3044. https://doi.org/10.3390/app12063044

Chicago/Turabian Style

Benitez, Ana R., Dani Margalit, Marklen Ryskin, Maoz Dor, Uri Shuali, Shlomo Nir, Tamara Polubesova, Julius Ben-Ari, Jeny Kertsnus-Banchik, and Tomas Undabeytia. 2022. "Modified Compositions of Micelle–Clay and Liposome–Clay Composites for Optimal Removal from Water of Bacteria and Hydrophobic Neutral Chemicals" Applied Sciences 12, no. 6: 3044. https://doi.org/10.3390/app12063044

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