Hexadecylpyridinium surfactant modified zeolite A as an active component of a polymeric membrane sulfite selective electrode

Physical and hydraulic properties of bioretention substrate using hexadecyl trimethyl ammonium bromide (HDTMA) modified zeolite

This study using hexadecyl trimethyl ammonium bromide (HDTMA) modified zeolite as a component of bioretention substrate, to investigate the effect of HDTMA modification on the basic physical and hydraulic properties of substrate layer. Two different levels of HDTMA modified zeolite (ZHD10 and ZHD50) were mixed with a mixture consists of peat soil, river sand and compost (fixed volumetric proportion at 5:4:1) with varying volumetric percentage (25%, 50%, and 75%) to form substrate media. The modification only changes the physical properties of zeolite and media with zeolite slightly, while significant changes in surface hydrophobicity and hydraulic properties were observed. A distinct decline of saturated hydraulic conductivity (K s ) values of zeolite can be observed after the modification, K s values drop 36.5% for ZHD10 and 55.1% for ZHD50. In contrast, K s values of substrate media using zeolite increase after the modification at the same volumetric ratio of zeolite. When 50% of zeolite (v/v%) was used in substrate, K s for natural zeolite, ZHD10 and ZHD50 was 0.024, 0.038 and 0.075 cm/s, respectively. Such alterations in K s are associated with the changes of surface hydrophobicity after the modification and ion exchange between modified zeolite and other materials after soaking into water. Changes in water retention characteristics (WRC) curves were in good accord with the variations in K s , and can be interpreted by the changed K s of tested materials. The orientations of HDTMA molecules loaded on zeolite surface were suggested to play crucial roles in altering the hydraulic properties of zeolite added substrate.

Comparison of Nature and Synthetic Zeolite for Waste Battery Electrolyte Treatment in Fixed-Bed Adsorption Column

To support a sustainable energy development, CO2 reduction for carbon neutralization and water-splitting for hydrogen economy are two feasible technical routes, both of which require a significant input of renewable energies. To efficiently store renewable energies, secondary batteries will be applied in great quantity, so that a considerable amount of energy needs to be invested to eliminate the waste battery electrolyte pollution caused by heavy metals including Cu2+, Zn2+ and Pb2+. To reduce this energy consumption, the removal behaviors of these ions by using clinoptilolite and zeolite A under 5, 7 and 10 BV h−1 in a fixed-bed reactor were investigated. The used zeolites were then regenerated by a novel NH4Cl solution soaking, coupled with the ultrasonication method. Further characterizations were carried out using scanning electron microscopy, N2 adsorption and desorption test, and wide-angle X-ray diffraction. The adsorption breakthrough curves revealed that the leaching preference of clinoptilolite was Pb2+ > Cu2+ > Zn2+, while the removal sequence for zeolite A was Zn2+ > Cu2+ > Pb2+. The maximum removal percentage of Zn2+ ions for clinoptilolite under 5 BV h−1 was 21.55%, while it was 83.45% for zeolite A. The leaching ability difference was also discussed combining with the characterization results. The fact that unit cell stayed the same before and after the regeneration treatment approved the efficacy of the regeneration method, which detached most of the ions while doing little change to both morphology and crystallinity of the zeolites. By evaluating the pH and conductivity changes, the leaching mechanisms by adsorption and ion exchange were further studied.

Utilization of rice husk and waste aluminum cans for the synthesis of some nanosized zeolite, zeolite/zeolite, and geopolymer/zeolite products for the efficient removal of Co(II), Cu(II), and Zn(II) ions from aqueous media

In this paper, rice husk and waste aluminum cans were exploited as silicon and aluminum sources, respectively for the low-cost synthesis of some nanosized zeolite, zeolite/zeolite, and geopolymer/zeolite products. XRD confirmed that the synthesized geopolymer/zeolite products are geopolymer/zeolite A (has a crystallite size of 58.44 nm & abbreviated as G1) and geopolymer/faujasite (has a crystallite size of 25.58 and 20.26 nm & abbreviated as G2 and G3, respectively). Also, the synthesized zeolite products are sodium aluminum silicate hydrate (has a crystallite size of 27.65 and 41.85 nm & abbreviated as H1 and H2, respectively). Besides, the synthesized zeolite/zeolite product is sodium aluminum silicate hydrate/zeolite A (has a crystallite size of 66.01 nm and abbreviated as H3). Moreover, the synthesized products were characterized using other tools such as HR-TEM, FE-SEM, EDX, and FT-IR. The synthesized products were efficiently applied for removing Co(II), Cu(II), and Zn(II) ions from aqueous media and wastewater which was taken from Abuzaabal- Qalyubiyah-Egypt. The maximum uptake capacity of G3 sample toward Co(II), Cu(II), and Zn(II) ions is 134.24 ± 1.26, 126.26 ± 0.32, and 131.93 ± 0.87 mg/g, respectively. The uptake of the studied metal ions is spontaneous, chemical, exothermic, and fitted well with the Langmuir isotherm and pseudo-2nd-order kinetic model.

Efficient recovery of Cu(II) by LTA-zeolites with hierarchical pores and their resource utilization in electrochemical denitrification: Environmentally friendly design and reutilization of waste in water

Water pollution seriously endangers human health and the environment. Here we prepared and tested mesoporous LTA zeolites for the adsorption of Cu(II) from aqueous media and the captured copper was further used for electrochemical nitrate reduction. The prepared hierarchically porous LTA exhibited a high capacity (341.5 mg g^-1) for Cu(II) adsorption, following the pseudo-second-order kinetic and Freundlich adsorption isotherm models well. The Cu-LTA sample was characterised by various analytical methods, and Cu(I) species were identified as the active sites for nitrate electrochemical reduction. Based on the spectral characterization and reducibility, strong metal-support interaction was found between copper and LTA, which is beneficial to the dispersion of active sites and their contacts with nitrates. In total, 10.1 g-N-NO₃ g^-1-Cu was reduced over the Cu-LTA-modified cathode in a three-electrode system with high N₂ selectivity (92.1 %). Compared to purely microporous zeolites, mesoporous LTA has a higher capacity for Cu(II) removal and nitrate reduction. The mesoporous structure allows easy access to the inner active sites with low diffusion resistance. The low Tafel slope and high current density confirm the high activity of the mesoporous Cu-LTA, making it a promising and efficient material for the removal and reuse of heavy metal ions.

Enhanced fluoride removal by hierarchically porous carbon foam monolith with high loading of UiO-66

Environmental concern associated with excess fluoride has intrigued the unceasing exploration of new multifunctional hybrid materials to mitigate any undesirable consequence to human health. Herein, a novel hybrid monolith has been successfully fabricated via a facile in-situ growth strategy for highly efficient defluoridation from contaminated waters, in which homogeneously dispersed UiO-66 particles are perfectly anchored on three dimensional (3D) porous carbon foam (CF). Benefiting from fully exposed active sites, excellent pore accessibility and efficient mass transport, the integrated UiO-66/CF hybrid monolith exhibits fast adsorption kinetics, and outstanding uptake capacity toward fluoride as high as 295 mg g^-1, which greatly outperforms the previously reported adsorbents. Furthermore, the fluoride removal efficiency of the spent monolith can reach up to 70% after four cycles, accompanied by facile separation nature and outstanding water stability. More significantly, the resulting UiO-66/CF packed column (0.36 g) can continuously treat 400 mL of F^- solution with 6.2 mg L^-1 before the breakthrough point occurs, highlight its potential feasibility for fluoride removal in the practical applicability.

Influence of the chain length of surfactant in the modification of zeolites and clays. Removal of atrazine from water solutions

Removal potentials of a surfactant modified zeolite (SMZ) and clay (SMC) for atrazine adsorption were evaluated. Materials were modified with hexadecyl trimethyl ammonium bromide (HDTMA-Br) and benzyl octadecyl dimethyl ammonium (BODA) chloride considering the critical micellar concentration (CMC) of each one (0.94 and 0.041 meq/L, respectively). The influence of the surfactant was analyzed in detail, particularly the formation of surfactant layers (complete or partial) connected with the length of the surfactant tail (16 and 18 methyl groups or number of carbons in the chain). Raw materials were characterized by XRD and Fourier transform infrared spectroscopy (FTIR), SMZ and SMC were analyzed by FTIR. Results obtained from kinetic adsorption experiments shown that equilibrium time is less for materials modified with HDTMA (8 h) than materials with BODA (10 and 12 h). Materials modified with the largest chain surfactant (BODA) showed more resistance to atrazine masse transference. The chemisorption was presented in the adsorption mechanisms of atrazine and adsorbent materials. Based on the results of adsorption isotherms Langmuir isotherms showed the better correlation coefficients value. The q_max is greater for materials modified with BODA (0.9232 and 4.2448 mg/g) than for materials modified with HDTMA (0.6731 and 3.9121 mg/g). Therefore, SMZ and SMC modified with the largest chain surfactant has more affinity for the pesticide. The removal process at high concentration of atrazine depends of the partition process but at lower concentration, it occurs not only by this process but also by absorption process.

Valorization of vitreous China waste to EMT/FAU, FAU and Na-P zeotype materials

In this study, Na-X, Na-P, SOD and EMT/FAU zeotype materials have been prepared from vitreous China waste by conventional hydrothermal route and alkaline fusion prior to hydrothermal synthesis. The conventional route has shown its limits in the activation of the waste in the chosen experimental conditions, [NaOH] = 3.5 M and T = 60 °C. The amorphous phase of vitreous China waste plays an important role during the zeolitization process because it easily dissolves into the alkaline solution compared to crystalline phases like quartz and mullite. By the conventional route, Na-X and Na-P1 and SOD zeolites were obtained. The alkaline fusion step using NaOH as mineralizer at 550 °C converted the waste to highly active soluble aluminate and silicate salts. The fused material was mixed with distilled water to have liquid to solid ratio L/S = 5, under vigorous stirring at room temperature for 1 day. The obtained gel with molar composition of 7.0 Na₂O: 1.0 Al₂O₃: 4.8 SiO₂: 209.4 H₂O was converted by hydrothermal crystallization at 60 °C to nanosized EMT/FAU zeotype and geopolymeric amorphous aluminosilicate material. With the increase of fusion time, there is a decrease of the amount of EMT-type zeolite.

Mechanism and performance for adsorption of 2-chlorophenol onto zeolite with surfactant by one-step process from aqueous phase

To decrease the power, material, and time consumption in wastewater treatment, a one-step process was performed to remove 2-chlorophenol (2-CP) from aqueous phase using zeolite and cetyltrimethylammonium bromide (CTAB). Compared with the traditional two-step process, the one-step process used in this study achieved almost eight times higher 2-CP adsorption capacity within a shorter time and maintained high removal efficiencies (around 65%) in reuse tests, thus becoming an efficient and economically acceptable alternative process. For the one-step process, the kinetic data fitted well with a nonlinear pseudo-second-order model, and the isotherm data fitted well with the Dubinin-Astakhov (DA) model. The uptake of 2-CP was highly dependent on pH, increasing in the pH range of 3-6. The enhanced 2-CP removal in a one-step adsorption process can be explained by the larger amount of surfactant loading (≥0.056mmol/g), as determined from the total organic carbon (TOC) and zeta potential. Due to the formation of a loose CTAB bilayer, the hydrophobic partition and the interaction with the positively charged "head" of CTAB bilayers were decisive for the enhancement of pollutant adsorption. Therefore, organic pollutants could be removed from water alongside the synthesis of hydrophobic zeolite in a one-step process, which is a promising technology for the in-situ treatment of organic wastewater.

A novel cysteine sensor based on modification of carbon paste electrode by Fe(II)-exchanged zeolite X nanoparticles

An electrochemical sensor based on carbon paste electrode (CPE) modified with iron(II) doped into a synthesized nano-particles of zeolite X (Fe(II)-NX/ZCME) was constructed, which is highly sensitive for detection of cysteine (Cys). The modified electrode showed an excellent electro-activity for oxidation of Cys in phosphate buffer at pH7.4. It has been found that anodic peak potential of Cys oxidation, compared with the unmodified CPE (UCPE), was shifted towards negative values at the surface of the modified electrode under the optimum condition. The peak current increased linearly with the Cys concentration in the wide range of 5.0 × 10(-9)-3.0 × 10(-3) mol L(-1). The very low detection limit was obtained to be 1.5 × 10(-10) mol L(-1). Finally, the modified electrode was used as a selective, simple and precise new electrochemical sensor for the determination of Cys in the real samples, such as pharmaceutical and biological fluids.

Design and characterization of chitosan/zeolite composite films--Effect of zeolite type and zeolite dose on the film properties

Chitosan films can be used as wound dressings for the treatment of chronic wounds and severe burns. The antimicrobial properties of these films may be enhanced by the addition of silver. Despite the antimicrobial activity of silver, several studies have reported the cytotoxicity as a factor limiting its biomedical applications. This problem may, however, be circumvented by the provision of sustained release of silver. Silver zeolites can be used as drug delivery platforms to extend the release of silver. The objective of this study was to evaluate the addition of clinoptilolite and A-type zeolites in chitosan films. Sodium zeolites were initially subjected to ion-exchange in a batch reactor. Films were prepared by casting technique using a 2% w/w chitosan solution and two zeolite doses (0.1 or 0.2% w/w). Films were characterized by thermal analysis, color analysis, scanning electron microscopy, X-ray diffraction, and water vapor permeation. The results showed that films present potential for application as dressing. The water vapor permeability is one of the main properties in wound dressings, the best results were obtained for A-type zeolite/chitosan films, which presented a brief reduction of this property in relation to zeolite-free chitosan film. On the other hand, the films containing clinoptilolite showed lower water vapor permeation, which may be also explained by the best distribution of the particles into the polymer which also promoted greater thermal resistance.