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

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 (0.169. mmol/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; 1. g iron can adsorb 17.5. mmol perchlorate. Results demonstrate that Fe-GAC is a promising sorbent for control of perchlorate pollution in drinking water and groundwater.