Layered double hydroxide (LDH) is one of the promising clay minerals that show great potential in various applications owing to its versatile structural properties. Prominently known for its high anion exchange capacity, this allows LDH to be considered as one of the most effective adsorbents in removing anionic toxic. However, the structural property of LDH hinders it from removing cationic toxic. Therefore, LDH have been functionalized to enhance its adsorption properties. In the present work, we aim to summarize the recent progress of functionalized LDH with different compounds for removal of both anionic and cationic toxics. The adsorption isotherm and effect of pH on absorption capacity also have been briefly reviewed.
Increasing problems with antibacterial agent primarily bacterial resistance and environmental pollution due to the high release of antibacterial agents in water necessitates the development of new and effective antibacterial agents. One of the techniques that can be used to overcome these problems is by immobilizing antibacterial compounds or any related compounds on the carrier system such as by using zeolite. In this study, zeolite Y was synthesized from rice husk ash as silica source by using hydrothermal technique and it was used as a carrier system for antibacterial copper (Cu) ions. A series of Cu-exchanged zeolite Y was then prepared by loading with different concentrations of Cu ions (100 ppm, 600 ppm and 900 ppm of the Cu(NO3)2) on the synthesized zeolite Y. The Cu-exchanged zeolite Y was characterized by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). These characterization techniques showed that the zeolite Y was synthesized in pure phase and had a good degree of crystallinity. Whereas, from the characterization results, zeolite Y was successfully loaded with different concentrations of Cu ions and no structural changes happen after modification. The antibacterial activity of the samples was determined through disc diffusion technique (DDT) against Gram positive bacteria (Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 29212) and Gram negative bacteria (Escherichia coli ATCC 11229 and Pseudomonas aeruginosa ATCC 15442). Based on the antibacterial results, the synthesized zeolite Y loaded with 900 ppm of Cu2+ showed the highest antibacterial activity compared to that of loaded with 100 ppm and 600 ppm of Cu2+. The higher the Cu concentration on the zeolite Y resulted in the higher antibacterial activity against wide spectrum of bacteria. As a conclusion, synthesized zeolite Y from rice husk ash could be a carrier system for antibacterial Cu ions and it has the potential for the application as antibacterial agents.
This study deals with the synthesis of zeolite from natural kaolinite using hydrothermal treatment and evaluation of its phase transformation behaviors. The synthesized zeolites were modified with silver ion by using the ion exchange method for the enhancement of antibacterial properties. The characterizations were performed by using X-ray diffraction spectroscopy, Fouriertransform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray. Disk diffusion technique (DDT) was used for the evaluation of the antibacterial property of the modified zeolites. This study observed the transformation of kaolinite into amorphous metakaolin after calcination treatment at 900 C and the successful reconstruction of amorphous metakaolin into synthesized crystal zeolite in the presence of sodium hydroxide as an activating agent. It was also found that the zeolite type A was produced at 100 C, while sodalites were produced at 120 and 140 C. DDT analysis revealed that the modified zeolites showed significant antibacterial capability against Escherichia coli ATCC 11229 and Staphylococcus aureus ATCC 6538. In general, the present study has proven that the zeolites can be synthesized from natural material and can be modified with silver ion to enhance their antibacterial activity.
In this study, the simultaneous action of surfactant modified clinoptilolite (SMC) as adsorbent for dyes and its antibacterial activity was investigated. Methylene blue (MB) and acid orange 7 (AO7) represent cationic and anionic dyes, respectively were used as adsorbate in this study and the antibacterial activity was studied against Gram-negative (Escherichia coli ATCC 11229) and Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 2921). Initially, natural zeolite clinoptilolite was modified with 3 different concentrations (0.1, 1.0 and 4.0 mM) of cationic surfactant hexadecyltrimethyl ammonium bromide (HDTMA-Br). The SMC samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), amount of HDTMA adsorbed and dispersion behaviour. Result from XRD shows that the HDTMA-Br molecules caused no effect on primary structure of the clinoptilolite since the clinoptilolite structure remained the same after modification with HDTMA-Br. Compared to the unmodified clinoptilolite, FTIR spectra of the SMC shows peak corresponds to C-H stretches which proved the attachment of HDTMA onto the clinoptilolite surfaces. In the dispersion behaviour study, SMC samples were located at the adjacent phase between the water and oil mixture. The amount of HDTMA-Br adsorbed onto the clinoptilolite increased with the increasing concentrations of the surfactant. The use of SMC as adsorbent and antibacterial agent were further studied against the ionic dyes and bacteria simultaneously. The results show that the adsorption capacity of SMC towards both ionic dyes increase with the increasing HDTMA-Br concentration. While for the antibacterial activity, the number of colony forming unit of bacteria seem to be highly reduced at the highest concentration of the HDTMA (4.0 mM) attached on the clinoptilolite. Hence, this study had shown that SMC has high adsorption capacity towards the ionic dyes at the same time reducing the growth of both Gram positive and negative bacteria in aquoes solution.
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