Preparation of Si@Al adsorbent and its adsorption properties for cadmium and lead in water
To prepare an adsorbent with low cost and high efficiency,which can simultaneously remove cadmium(Cd)and lead(Pb)from water,Si@Al adsorbent was prepared by using electroflocculating precipitated waste as raw material,mixing with sodium silicate at a mass ratio of 4∶1 and calcining at 200℃for 2 h.The preparation method was"simple and easy,turning waste into treasure".The results of the adsorbent characterization and pollutant adsorption experiment showed that Si@Al adsorbent had uniform particles,distinct layers,loose porous appearance,and the internal structure was scattered without a crystal structure.The optimal adsorption conditions for Cd were as follows:the amount of adsorbent was 3.0 g/L,the reaction time was 10 min,the pH was 4.5,and the removal rate was up to 95.26%.The optimal adsorption conditions for Pb were as follows:adsorbent dosage 1.0 g/L,reaction time 30 min,pH=8.5,and the highest removal rate of 99.95%.Based on the results of thermodynamics,kinetics and zero potential point,it could be seen that the adsorption of Pb was a single-layer homogeneous chemical adsorption behavior,while the adsorption of Cd was a multi-layer heterogeneous chemical adsorption behavior.The adsorption mechanisms included complexation,ion exchange,surface deposition and electrostatic attraction.
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