Removal of malachite green (MG) from aqueous solutions by native and heat-treated anaerobic granular sludge

The performance of native and heat-treated anaerobic granular sludge in removing of malachite green (MG) from aqueous solution was investigated with different conditions, such as pH, ionic strength, initial concentration and temperature. The maximum biosorption was both observed at pH 5.0 on the native and heat-treated anaerobic granular sludge. The ionic strength had negative effect on MG removal. Kinetic studies showed that the biosorption process followed pseudo-second-order and qe for native and heat-treated anaerobic granular sludge is 61.73 and 59.17 mg/g at initial concentration 150 mg/L, respectively. Intraparticle diffusion model could well illuminate adsorption process and faster adsorption rate of native anaerobic granular sludge than heat-treated anaerobic granular sludge. The equilibrium data were analyzed using Langmuir and Freundlich model, and well fitted Langmuir model. The negative values of ΔG° and ΔH° suggested that the interaction of MG adsorbed by native and heat-treated anaerobic granular sludge was spontaneous and exothermic. Desorption studies revealed that MG could be well removed from anaerobic granular sludge by 1% (v/v) of HCl–alcohol solution.