Effect of preparation protocol on anchoring quaternary ammonium/epoxide-forming compound into granular activated carbon for perchlorate adsorption: Enhancement by Response Surface Methodology

A novel method has been developed for anchoring quaternary ammonium/epoxide-forming compounds (QAEs) within bituminous based granular activated carbons (GACs). This modified GAC was then used to remove perchlorate from groundwater. The effect of the preparation temperature (T), solution pH (pH) and the dry mass ratio of QAE-to-GAC (R) over the perchlorate adsorption capacity (Qe) were studied by the Response Surface Methodology. The combined effects of these variables were fitted to a quadratic model to determine the more favorable preparation protocol for perchlorate removal. Statistical analysis revealed that: (1) the interaction of T and pH incurred the most effect on Qe; and (2) two of the more favorable preparation protocols became apparent: one was at 75 °C, pH 11 and R of 1.73 g QAE/g GAC (U17), the other was at 35 °C, pH 14 and R of 4.00 g QAE/g GAC (U2). Rapid small scale column tests were further employed to evaluate the performance of the QAE-anchored GACs for perchlorate removal. U17 and U2 exhibited 18–20 times longer bed life (BV) to 6 ppb breakthrough than did the Pristine GAC (900 BV), when processing groundwater that had been spiked with 30–35 ppb perchlorate. This indicated the statistical method enhanced GAC’s perchlorate removal efficiency.