Efficient removal of uranium from wastewater using pig manure biochar: Understanding adsorption and binding mechanisms

In this work, three kinds of biochars (PMBC-H2O, PMBC-PP and PMBC-HP) with excellent adsorption performance were obtained by carbonizing pig manure pre-treated with different agents. These biochars had the ordered mesoporous structures and possessed abundant active functional groups on their surface. The adsorption behaviors of the biochars towards UVI under various conditions were evaluated by batch experiment. The results showed that KMnO4 and H2O2 could enormously improve the adsorption performance of PMBC to UVI. After KMnO4 and H2O2 pretreatment, the maximum adsorption capacities of PMBC-PP (979.3 mg/g) and PMBC-HP (661.7 mg/g) were about 2.6 and 1.8 times higher than that of PMBC-H2O (369.9 mg/g), respectively, which was much higher than previously reported biochar-based materials. Obviously, KMnO4 pretreatment leaded to a higher enhancement than that of H2O2. The removal mechanism of UVI on PMBC-PP was discussed in-depth. The interaction between UVI species and PMBC-PP was mainly ascribed to the abundant active sites on the surface of PMBC-PP. In a word, conversion of pig manure pre-treated with KMnO4 into biochar not only demonstrates that PMBC-PP has great potential in the treatment of actual uranium-containing wastewater, but also provides a method for the rational utilization of pig manure to reduce the pollution.