The antibacterial activity of regenerated NaY zeolite (thermal treatment from cetyltrimethyl ammonium bromide (CTAB)-modified NaY zeolite and pretreatment with Na ions) loaded with silver ions were examined using the broth dilution minimum inhibitory concentration (MIC) method against Escherichia coli (E. coli ATCC 11229) and Staphylococcus aureus (S. aureus ATCC 6538). X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and chemical elemental analyses were used to characterize the regenerated NaY and AgY zeolites. The XRD patterns indicated that the calcination and addition of silver ions on regenerated NaY zeolite did not affect the structure of the regenerated NaY zeolite as the characteristic peaks of the NaY zeolite were retained, and no new peaks were observed. The regenerated AgY zeolite showed good antibacterial activity against both bacteria strains in distilled water, and the antibacterial activity of the samples increased with increasing Ag loaded on the regenerated AgY zeolite; the regenerated AgY zeolite was more effective against E. coli than S. aureus. However, the antibacterial activity of the regenerated AgY was not effective in saline solution for both bacteria. The study showed that CTAB-modified NaY zeolite materials could be regenerated to NaY zeolite using thermal treatment (550°C, 5h) and this material has excellent performance as an antibacterial agent after silver ions loading.
In this work, the novel imprinted zeolite (IZ) was synthesized, and its properties and performance in terms of adsorption of p-Cresol, which represent the protein-bounded uremic toxins in aqueous phase under phosphate buffer saline, were studied and compared with the synthesized zeolite-Y (ZeoY-S) and commercial CBV 100 zeolite-Y (ZeoY-C). The ZeoY-S was synthesized from sodium aluminate, NaOH, H2O and SiO2 under aging for 24 h at room temperature and hydrothermal condition for 24 h at 100 °C, with an initial composition of 10SiO2:Al2O3:4Na2O:180H2O. The ZeoY-S has been modified by using the imprinting technology to produce the IZ via the use of p-Cresol as a template. The p-Cresol successfully imprinted on the zeolite-Y was proved through the multipoint Brunauer-Emmett-Teller (BET) and the performance of IZ that was compared to ZeoY-S and ZeoY-C. Based on the BET results, it proves that the pore size of IZ is in accordance with the target compound, which is p-Cresol at 0.79 nm. This modification was able to adsorb p-Cresol 2.5 and 3.5 times higher than ZeoY-S and ZeoY-C can, respectively. Langmuir and Freundlich adsorption isotherm models, together with the pseudo-first and -second order and intra-particle diffusion kinetics models, were used to investigate the adsorption behavior of p-Cresol on the zeolites. The IZ has 4.30 times greater competitive molecules than ZeoY-S and the properties of IZ were not influenced by the content of other phenolic group uremic toxins as competitive molecules. It can be concluded that the micropores of zeolite as adsorbent can be modified using the imprinting technology in order to increase its sensitivity and selectivity towards p-Cresol.
Forward osmosis (FO) has been recognized as the preferred alternative membrane-based separation technology for conventional water treatment technologies due to its high energy efficiency and promising separation performances. FO has been widely explored in the fields of wastewater treatment, desalination, food industry and bio-products, and energy generation. The substrate of the typically used FO thin film composite membranes serves as a support for selective layer formation and can significantly affect the structural and physicochemical properties of the resultant selective layer. This signifies the importance of substrate exploration to fine-tune proper fabrication and modification in obtaining optimized substrate structure with regards to thickness, tortuosity, and porosity on the two sides. The ultimate goal of substrate modification is to obtain a thin and highly selective membrane with enhanced hydrophilicity, antifouling propensity, as well as long duration stability. This review focuses on the various strategies used for FO membrane substrate fabrication and modification. An overview of FO membranes is first presented. The extant strategies applied in FO membrane substrate fabrications and modifications in addition to efforts made to mitigate membrane fouling are extensively reviewed. Lastly, the future perspective regarding the strategies on different FO substrate layers in water treatment are highlighted.