Removal of bromate from water using surfactant modified powdered activated carbon(SM-PAC)

Abstract

Powder activated carbon was modified with three different cationic surfactants; Cetylpridinium chloride (CPC), Hexadecyltrimethyl-ammonium bromide (CTAB) and Hexadecyltrimethyl-ammonium chloride (CTAC) for bromate removal from water. Modification of powdered activated carbon with cationic surfactants enhanced the positive charge on the activated carbon surface. Zeta potential values for surfactant modified powder activated carbon(SM-PAC) with CPC, CTAC and CTAB were 52.45mv, 50.85mv and 44.45mv respectively. However that increased in zeta potential slightly decreased the B.E.T surface area of surfactant modified powdered activated carbon(SM-PAC).Cationic surfactant adsorption on powder activated carbon (PAC) was dependant on activated carbon surface functional group, surfactant organic chain length and presence of counter ion on the surfactant .Surfactant having large number of CH2 - group like CPC showed high adsorption on PAC surface(1.32mmol/g) than that of CTAC(0.82mmol/g) and CTAB(0.95mmol/g) with smaller chain length. Surfactant with Br- as counter ion like CTAB showed high adsorption than its counterpart with Cl- as counter ion like CTAC. Among the surfactant, 1.132 mmole/gm of CPC was adsorbed while CTAC and CTAB had 0.80 and 0.92mmole/gm of adsorption on PAC respectively. Temperature effect the modification process of PAC with surfactant. In case of CPC, amount of surfactant adsorbed decrease with increase in temperature while for CTAC and CTAB, adsorption increase with increase in temperature. Maximum bromate removal was attained in case of CTAC modified SM-PAC due to high zeta potential value of SM-PAC and Cl- as counter-ion. Main mechanism for bromate removal is electrostatic interaction and ion-exchange. So counter -ion on the surfactant played an important role. In case of Cl- as counter ion, bromate removal is higher than that of Br- as counter ion on surfactant. SM-PAC modified with CTAC had 35.742mg/g of bromate adsorption capacity while SM-PAC...