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Swine manure char as an adsorbent for mitigation of p-cresol



There is a significant interest in synthesizing inexpensive adsorbents for mitigating pollutants emitted from animal agriculture industry such as p-cresol. Biochar, a byproduct obtained from thermochemical biomass processing is one such source of adsorbent materials. However, presently there is not enough quantitative information on adsorption of p-cresol on biochar. Hence, the goal of this research is to investigate swine manure char as an inexpensive adsorbent for removal of p-cresol from an aqueous system. Swine manure was gasified for 15 min at 704°C to obtain gasified manure char. The char was characterized using physical and chemical techniques. Batch experiments were performed in duplicates at 25°C, 35°C, and 45°C to determine the adsorption isotherms and kinetics. Results indicated that gasification enhanced surface area and acid value of manure from 11.42 ± 0.20 to 49.12 ± 0.79 m2 g−1 and 7.81 ± 0.05 to 8.57 ± 0.01, respectively. The enhanced basicity of the resultant char promoted chemisorption of p-cresol on char surface with maximum adsorption capacities of 7.63 mg g−1 (25°C), 14.99 mg g−1 (35°C), and 14.84 mg g−1 (45°C). Langmuir and Freundlich models suggested that adsorption of p-cresol on char was favorable. Kinetic analysis of the data also confirmed chemisorption of p-cresol while the analysis of transport processes suggested that internal diffusion of p-cresol within the pores was the rate-limiting step. Use of biochar as an adsorbent for p-cresol will add value to gasification byproducts and simultaneously reduce water and air pollution associated with swine farming operations. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 125–131, 2015