Nanoscale iron hydroxide-doped granular activated carbon (Fe-GAC) as a sorbent for perchlorate in water

Abstract

In this study, a new nanoscale iron hydroxide-doped granular activated carbon (Fe-GAC) was synthesized, characterized, and tested for adsorption of perchlorate ClO4- in water. XPS, FTIR and SEM analysis showed that nanoscale rod-shape iron hydroxide, in addition to sulfate, covered on the GAC-Fe surface. Solution pH and iron content were two key factors controlling the treatment efficiency. Acidic condition generally favored the adsorption, and the optimal pH range for perchlorate adsorption was 2–3. The highest perchlorate adsorption capacity was achieved by Fe (0.97)-GAC (0.169mmol/g) with an iron content of 0.97%wt. of GAC. More or less iron content in the sorbent lowered the perchlorate adsorption capacity. The three common anions, Cl-,SO42- and NO3-, all slowed down the perchlorate adsorption, with an order in terms of their inhibition effects NO3->SO42->Cl-. Electrostatic attraction, ion exchange, and surface complexation contributed to the perchlorate adsorption. Particularly, the first two mechanisms (outer-sphere adsorption) were more dominant, accounting for ∼76% of perchlorate removal. Nano-hydroxy iron containing SO42- uniform distributed on GAC can provide considerable active sites for perchlorate and have a high adsorption capacity; 1g iron can adsorb 17.5mmol perchlorate. Results demonstrate that Fe-GAC is a promising sorbent for control of perchlorate pollution in drinking water and groundwater.