Study on heavy metal removal performance of different ceramic nano-composite tubular membrane

Abstract

The experimental investigation was carried out to study the removal of heavy metal contaminations from drinking water by synthesizing the mesoporous Mg–Al–Ti composite oxide nanoparticles and incorporating them into three different MMM layers on ceramic membranes. There are many heavy metals present in drinking water but we focused on arsenic, chromium, cadmium, and lead removal. Heavy metals have many adverse effects on the human body when consumed. There are many water purification techniques available such as Reverse Osmosis, Ultra-filtration, Microfiltration, and Nano-filtration for removing heavy metal contaminants from drinking water still none can remove arsenic efficiently from drinking water. The permissible limit of arsenic in drinking water is 10 ppb. Yet, a single process has not been developed that can bring arsenic-contaminated drinking water into the permissible limit suggested by the World Health Organization (WHO). Unlike other heavy metal removal methods, adsorption removes 95 % of arsenic from drinking water which is the highest removal rate in all available water purification techniques. Hence, we have chosen the adsorption process in the arsenic removal study. The planned methods are the synthesis of the PSF blend membrane, the In-situ formed membranes, and the PVA membrane by sol-gel method. The arsenic removal performances can be determined by characterization of all three mixed matrix membranes. After doing several tests like heavy metal ions competition, FESEM analysis, XRD analysis, contact angle, pure water flux, pH testing, anti-fouling test, long-term filtration, regeneration, and anti-bacterial property test. We concluded that NPs adsorption capacity for multi-metal (As, Pb, Cr, Cd) ions in binary, ternary, and total heavy metal batch setup shows excellent removal % (> 80 to 90 %) in all concentrations. The Arsenic adsorption properties of NPs incorporated MMMs in the effect of pH showed a 99 % removal percentage in all ranges of pHs. Membrane contact angles 25.06º (In-situ), 69.83º (PSF), and 35.58º (PVA) state the hydrophilic properties of the membranes. FRR 79 % of PSF, 87 % for In-situ, and 89.87 % for PVA membrane shows good anti-fouling properties of all MMMs. Long-term filtration shows a breakthrough volume of 4.5 L while filtering 100 ppb As a solution and the flux is declining with the addition of several filtration cycles. However after regeneration of the spent membrane, long-term filtration showed breakthrough volume of 2.5 L. The regeneration was confirmed with the increase in flux of the spent membrane. In the anti-bacterial property test in-situ membrane showed better results than the other two membranes, altogether all three MMMs showed good anti-bacterial properties. Successful positive inhibitory zone, > 99 % E.coli removal percentage, and > 99.99 % removal of colony forming units (CFU/ml) in the filtration process confirmed the anti-microbial resistance. With its multi-functionality, these membranes hold great potential for practical water treatment applications.