AC-EG adsorption treatment of pharmaceutical wastewater and adsorbents’ microwave regeneration

Abstract:

Aiming to treat pharmaceutical wastewater containing pollutants that are difficult to be biodegraded, and deal with the inhomogeneous temperature and big attrition rate during the microwave regeneration of activated carbon, this study adopted a method, using a mixture of activated carbon and expanded graphite as AC-EG adsorption materials, to adsorb and treat the wastewater of a pharmaceutical factory after biochemical treatment. Based on the component analysis of wastewater from a pharmaceutical company, the adsorption thermodynamics and dynamics mechanism of pollutants in pharmaceutical wastewater adsorbed by adsorption material was studied, and the effect of microwave regeneration was investigated. The results showed that the wastewater contained a variety of unbiodegradable pollutants like pyridine, amide, azole, pyrazine and so on. The removal rate of COD in wastewater reached 58.25% when adsorbent was a mixture of activated carbon and 15% expanded graphite. The adsorption process, which AC-EG with 15wt% expanded graphite adsorbed pollutants in pharmaceutical wastewater, is an exothermic physical adsorption which follows Freundlich model (ΔH=-16.918 kJ/mol), and its entropy reduced(ΔS=-54 J/(mol·K)). Its kinetics model was relatively consistent with the second-order equation. A mixture of activated carbon and expanded graphite was heated and adsorbed microwave radiation more uniformly. With the increase of expanded graphite's doping amount, the adsorbent regeneration rate increased and the attrition rate declined.