Efficiency evaluation of arsenic(III) adsorption of novel graphene oxide@ iron-aluminium oxide composite for the contaminated water purification

Prolong consumption of arsenic-rich drinking water causes serious health problem. Aiming to minimize the problem, it is attempted to develop cheap and advanced materials for arsenic extraction from the contaminated water. Thus, multifunctional graphene oxide (GO) -incorporated iron-aluminium mixed oxide (GIAMO) composite has been prepared with five different GO content, and evaluated by batch method for the arsenic(III) removal efficiency. Among the as-prepared GIAMO samples, three samples consisting 1.0, 2.0 and 3.0 g of GO show equally good (92-95%) arsenic(III) removal efficiency, which is 30-35% higher than pristine iron-aluminium oxide (IAMO) from an aqueous solution (5.0 mg As-III.L-1) at pH 7.0 (+/- 0.2) and 303 K. Thus, 1.0 g GO-inserted GIAMO (GIAMO-1) sample was characterized as microcrystalline (10-15 nm) with BET surface area about 1.45 times higher than IAMO and investigated for the arsenic(III) adsorption. Optimized pH for arsenic(III) adsorption is 6.0-8.0. The kinetic data agree more closely with pseudo-first order equation (R-2 = 0.98-0.99) than pseudo-second order equation (R-2 = 0.92-0.93). The equilibrium data describe the Langmuir isotherm (R-2 = 0.97-0.98) better than the Freundlich isotherm (R-2 = 0.91-0.92), showing the Langmuir monolayer capacity 42.2836 mg.g(-1) at 293 K which drops to 24.9170 mg.g(-1) at 313 K. High negative enthalpy change (Delta H degrees similar to -224 kJ. mol(-1)) is responsible for the spontaneous reaction (Delta G degrees = negative) despite unfavorable entropy change (AS = -0.71 kJ.mol(-1)). The order of competitive effect of PO43-, SO42- and HCO3- on arsenic(III) removal efficiency is PO43- > SO42- > HCO3-. However, the high HCO3- (> 200 mg.L-1) enhances the arsenic(III) removal efficiency of this material. 2.0 M NaOH can regenerate arsenic adsorbed GIAMO-1 only up to 50-60%. 0.65 g. of composite per L of high arsenic (As-total: 0.115 mg L-1) groundwater can upgrade to potable standard, encouraging possible safe use for high arsenic water treatment. Highly negative enthalpy change, poor regeneration, FTIR, XRD and CV analyses of arsenic-rich solid suggested that arsenic(III) is stabilized over the solid surface without oxidation by surface complex formation.