Kinetics of phosphate adsorption by Ca/Cr layered double hydroxide

Kinetics of phosphate adsorption by Ca/Cr layered double hydroxide (LDH) in a batch reactor was investigated in this study. The kinetic experiments indicated that the sorption of phosphate from the synthetic feed solution by the synthesised LDH was very fast, with over 98% removal being achieved within 5 min of contact. Kinetic modeling of the sorption process to different kinetic models (pseudo first order, pseudo second order, Elovich and intraparticle diffusion) showed that the pseudo-second order model best described the process. Studies of effect of hydrochemistry on the sorption process such as initial solution pH, ionic strength and organic load contamination interference, indicated nominal effect on the amount of phosphate removed by the LDH. Overall, the study indicated that chemisorption and precipitation are active contributory mechanisms to the sorption of phosphate by Ca/Cr LDH from solution.   Key words: Adsorption kinetics, chemisorption, layered double hydroxide, phosphate removal, precipitation.