Pilot-scale combined adsorption columns using activated carbon and zeolite for hazardous trace elements removal from wastewater of entrained-flow coal gasification

Abstract When entrained-flow gasification technology is applied on a large scale, the release of hazardous trace elements (HTEs) from the use of coal in gasification poses a potential threat to environmental and human health. An adsorption method combining granular activated carbon (GAC) and zeolite as adsorbents to remove the HTEs is proposed. A pilot-scale experiment proved that this method can effectively remove HTEs, especially, the removal rate for mercury and beryllium achieved 99 %. Additionally, adsorption studies using GACs were conducted through laboratory batch experiments employing several kinetic and isotherm models. The results show favorable levels of mercury, arsenic, and beryllium adsorption by GAC. GAC derived from low rank bituminous coal has the good comprehensive adsorption performance of HTEs. Langmuir presented the best fit of arsenic and beryllium adsorption, and Freundlich presented the best fit of mercury. The kinetics studies showed that experimental data follow Pseudo-second order. Zeolite’s capacity for ion exchange greatly affects its adsorption performance, which supplements the adsorption capacity of GAC for metal and metalloid ions. This study provides an approach that is fast, and easily integrates with existing processes for removing HTEs in entrained-flow coal gasification wastewater.