Mechanisms associated with the separation of phenols from complex coexisting systems

Abstract

Phenols are recognized as one of the major hazardous organic compounds in industrial wastewater. However, the effects of the coexisting substances on the elimination of the phenolic pollutants were less explored. Herein, we have systematically evaluated the adsorption processes of hydroquinone with respect to three adsorbents in acid, salt, and homolog systems. Our results demonstrated that low concentrations of coexisting acids could benefit the adsorption process with a maximum promotion rate of 143.4% (Qe from 74.3 to 180.9 mg/g), while high concentration of lactic acid resulted in considerable inhibition to St-DVB-nitro with a maximum inhibitory rate to 72.8% (Qe=20.2 mg/g). The coexisting salts exhibited a potentiation effect with a maximum promotion efficiency of 105.9% (Qe=153.0 mg/g). Competitive binding to adsorption sites could be observed in homolog coexisting system, where p-nitrophenol served as the dominant adsorbent and the hydroquinone adsorption capacity were only maintained at 45.4% (Qe=33.7 mg/g). On basis of the coexisting and preloading systems study, KCl could increase the force of mass transfer by salting-out effect and cation synergistic effect to promote the adsorption. Meanwhile, preloading experiments confirmed the competitive occupation effect of lactic acid and p-nitrophenol on the adsorption site, and the more hydrophobic p-nitrophenol could even desorbed hydroquinone (desorption rate 19.5–22.2%). This work on the interactions among phenols, coexisting factors and solid interfaces will guide the actual phenols wastewater treatment.