Simultaneous removal of cationic and anionic dyes by the mixed sorbent of magnetic and non-magnetic modified sugarcane bagasse.

Magnetic carboxyl groups modified (MMS) and non-magnetic amine groups modified (AMS) sugarcane bagasse were prepared and mixed to remove cationic and anionic dye simultaneously from aqueous solution. For comparison, the adsorption performances of MMS, AMS and the mixed sorbent for basic magenta (cationic dye) and congo red (anionic dye) were investigated in the binary system. Zeta potential analysis showed that MMS was negatively charged and AMS was positively charged in the investigated pH range. The adsorption capacities of MMS for basic magenta and congo red were 1.24 and 0.04mmolg(-1), while those of AMS were 0.04 and 1.55mmolg(-1), respectively. Both of MMS and AMS had high adsorption capacity and affinity toward opposite-charged dye but low adsorption capacity and affinity toward similar-charged dye. Adsorption experiments in the binary system showed that only the mixed sorbent could remove the two dyes simultaneously from aqueous solution (removal efficiencies >90%). The amounts of basic magenta and congo red absorbed on the mixed sorbent both increased linearly with the increase of their initial concentrations in the investigated range. The dye loaded mixed magnetic and non-magnetic sorbents could be separated by a magnet. MMS and AMS could be regenerated by using acid and alkaline eluents, respectively. After regeneration, the MMS and AMS could be mixed again and used repeatedly. The mixed sorbent had great potential in practical dye waste water treatment.