Synthesis of Metal Oxides and its Application as Adsorbent for the Treatment of Wastewater Effluents

Metal oxide particles by virtue of reduced particle size are gaining great importance due to its wide applications in almost each field. The treatment of waste water needs special attention as halogenated organics, nitrates, sulfates, phosphates, heavy metals and microorganisms in effluents are contributing to the pollution load. The present study is an attempt of synthesizing metal oxides and its composites to be used as catalysts for the removal of different pollutants discharged from various industries. Metal oxides of Fe and Ni have been synthesized by the standard method of co-precipitation. The method is preferred over the others for being simple and efficient giving a percentage yield of 80% and 63% for the synthesized Fe and Ni particles, respectively. The particle size ranges in diameter ~10-20nm and 40nm for iron and nickel particles, respectively. A composite of Fe and Ni in 1:1 molar ratio was also prepared by thorough mechanical grinding in agate pestle and mortar till fine, uniform, and blended powder. The characterization of synthesized materials confirmed the linkage of metal-oxygen and red shift through FTIR and UV-Visible spectroscopic technique, respectively. Sampling was done for three categories of water samples; industrial (five different industries), municipal and drinking water samples. Composite aqueous sample of each category was characterized for its physicochemical parameters like pH, EC, COD, and concentration of nitrates, sulphates, nickel, copper, cadmium and lead. The analysis presents the effluent sample of Leather industry exceeding the permissible limits significantly higher for nitrates, nickel, lead, and cadmium as compared to other effluents. Whereas municipal waste water samples depicted exceeding limits for Cu, Ni, Pb and Cd concentration. The synthesized metal particles were applied as adsorbents for the removal of different pollutants in batch experiments. The optimum removal efficiency of 97%, 96% and 98% for lead was achieved by Ni, Fe and composite particles, respectively. On comparison of efficiency of different adsorbents, Iron particles showed remarkably good efficacy for removal of metals in terms of attaining equilibrium in relatively short time (15 minutes). However, pollutants like sulphates and nitrates were more effectively reduced by Ni particles to 18 and 54 times less than the background concentration. Adsorption Kinetics and Equilibrium models were applied. The kinetics revealed pseudo second order relatively more fitted than pseudo first order. On the other hand, equilibrium models of Langmuir a