Activation of persulfate by different biochars for the degradation of sulfamethoxazole

Advanced oxidation processes (AOPs) based on persulfates have become very popular for in-situ water/wastewater treatment since persulfates are more stable and less costly than other oxidants such as hydrogen peroxide. The conversion of persulfates to sulfate radicals requires an activation agent, including transition metals, high temperature, ultraviolet irradiation, ultrasound irradiation, and microwaves. Recently, there have been several reports concerning the use of carbonaceous materials such as graphene, graphene oxide, carbon nanotubes, and activated carbons as persulfate activators. Biochars, the solid residue produced from biomass thermal decomposition with no or little oxygen at moderate temperatures, are low-cost materials with high surface area and desirable physicochemical properties in terms of pore size distribution, the number of functional groups, and minerals that can be employed as catalytic supports.

The aim of this work is to test whether biochar produced from malt spent rootlets (MSR) and olive kernels are suitable activators of persulfates for the degradation of sulfamethoxazole (SMX) under various operating conditions and aqueous matrices.  Olive kernels and MSR were pyrolyzed at 850 and 900^oC, respectively.  The actual matrix effect on degradation was minor and so was the effect of radical scavengers. Persulfate activation seems to occur on the biochar surface through interactions with the surface functional groups, generating radicals that are not released in the solution.