Development and applications of novel nanostructured materials in water treatment : adsorption, filtration, and reaction
Nanomaterial-based adsorbents and photocatalysts have gained increasing attention in the applications of water and wastewaters treatment due to their attractive properties and strong adsorption capabilities for a wide range of contaminants. The objective of this study is to fabricate, characterize, and apply a group of nanomaterials to adsorb, remove, and degrade contaminants in water. An iron oxide/graphene oxide (IOGOx) composite was evaluated for the effective As(V) removal from the aqueous solutions. Adsorption on hematite and IOGO(25 [percent]) at 25 [degrees]C, pH 7, and 1 mM NaNO3 showed 76 [percent] of As(V) removal within the first 5 minutes and 95 [percent] at 40 minutes. As(V) adsorption efficiency increased with increase GO loading; while, this efficiency decreased at high IO loading. Kinetic data was a well fitted to pseudo-second-order, so those results suggested that the surface complexation is the main mechanism for As(V) adsorption on the surface of adsorbents. All composites were able to reduce the As(V) concentration below 10 [micro]gL[superscript -1] that is the recommended maximum permissible concentration of As(V) in drinking water by World Health Organization (WHO). A novel technique for coating a group of tubular ceramic membranes by multi-layers of TiO2 was used to reduce the pore size of the support membranes and to improve their performances. Polyethylene glycol was used as a model molecule to compare and examine the coated membranes in the evolution of fouling and rejection over time. The SEM images showed that TiO2 covered the surface and the active layer; therefore, the permeable path sizes decreased gradually. The results of flux and permeability of membranes confirmed the success of the coating. The transmembrane pressure (TMP) increased with each coating layer, while the rejection of the membrane was improved. After cleaning the membranes with ultrapure water, TMP of all the membranes decreased until reaching to the clean material values. In this study, 4-layers coated membrane showed its ability to be used many times after cleaning with ultrapure water. The coated membranes were tested for a novel technique that combines filtration and advanced oxidation processes for sulfamethazine (SMZ) removal and degradation using a continues flow reactor and under different conditions. The system included a a membrane module with UV-light. In the absence of UV-light, the results showed no significant removal of 5 ppm and 10 ppm of SMZ during the experiment. Under UV-light, the system was able to significantly degrade 5 ppm and 10 ppm of SMZ from the solution, particularly, at pH 2. In the presence of humic acid (HA), there was a significant increase in the SMZ degradation with all pH values by decreasing the required time to degrade SMZ in clean water. When NO3[superscript −] or Cl[superscript −] ions were added, an increase in the degradation rate of SMZ was observed in the presence of NO3[superscript −] in comparison with clean water, but Cl[superscript −] led to a decrease in the SMZ degradation under UV light. The process could be applied for SMZ removal from the water in water treatment plants.