(205f) On the Choice of Batch or Fixed-Bed Adsorption Processes for Wastewater Treatment

Newly emerged nanomaterials, such as graphene or carbon nanotubes, are of increasingly widespread importance in environmental remediation, especially in their ability to remove undesirable chemicals from hydrological systems. Despite recent advances, the high cost of these materials and the relative inability to regenerate them hinders their use at larger scales. While it is commonly held that adsorption in fixed bed processes is more efficient than in batch processes, the definition of efficiency needs to be examined closely. When the goal is to remove all contaminants from a solution, fixed bed adsorption is the only process that may be used. However, the situation is distinctly different when there is a threshold level of effluent contamination—in such cases, a process may be chosen that maximizes the quantity of contaminant adsorbed per unit mass of adsorbent. In this paper, we show that there exists a critical effluent concentration above which batch processes are more efficient than fixed bed processes from this perspective. The present analysis is supported by results from previous literature for which comparisons are possible between fixed bed and batch process adsorption. This work proposes a simple method to choose either batch or fixed bed processes when the goal is to minimize the quantity of adsorbent needed to remove contaminants to below a specified threshold level. It also provides a systematic set of self-consistency checks on experimental measurements that may be used for comparative studies of these methods.