Removal of Zinc from wastewater using natural and synthetic adsorbents
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Several methods are utilized to remove zinc from industrial wastewater in which adsorption is the most versatile and widely used method. In the present work the ability of both natural and synthetic adsorbents were investigated to remove Zn(II) from wastewater. Neem bark, rice husk ash, clarified sludge and activated alumina were used for adsorption studies. The effect of different parameters such as contact time, solution pH, adsorbent dose and initial Zn(II) concentration were evaluated in terms of percent zinc removal. Clarified sludge, activated alumina and neem bark showed better adsorption behavior at acidic pH (5.0) whereas rice husk ash provided higher adsorption at alkaline pH(7.0-9.0) The equilibrium time was achieved after 5 h for rice husk ash and neem bark, 4 h for activated alumina and 2 h for clarified sludge. The kinetics of the Zn(II) adsorption on different adsorbents was found to follow first order rate mechanism. The highest and lowest rate constant was achieved for clarified sludge (22.85x10-2) and neem bark (0.28x10-2) respectively at 300C. Freundlich adsorption isotherm was well followed by all the adsorbents. Clarified sludge was the most effective adsorbent for Zn (II) removal. The optimum pH was 5.0 and equilibrium time was achieved after 2 h. First order rate equation and Freundlich adsorption isotherm was followed.