Fast pyrolysis biochar, a low cost material for the removal of phenoxy herbicides

M. Essandoh, D. Wolgemuth, C.U. Pittman Jr, D. Mohan, T. Mlsna
United States Department of Agriculture,
United States

Keywords: wastewater treatment, low cost adsorbent, adsorption, phenoxy herbicides, 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid


Abstract/Summary The removal of hazardous organic compounds from contaminated water is a critical issue facing the scientific community and society as a whole. The occurrence of these organic pollutants (e.g. pesticides) has caused a lot of concerns as a result of their potential negative effect on humans and the environment. Although activated carbon sorbent has the largest market share and remains the most popular industrial adsorbent for organic contaminants removal, it has several disadvantages. As the search for low cost materials have intensified, our study shows fast pyrolysis switchgrass biochar, a by-product from the bio-oil industry, to be an efficient sorbent for the removal of herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) from aqueous solution. The biochar was characterized using several techniques including scanning electron microscopy, surface area measurement, Fourier transform infrared, and point of zero charge. Batch experiments were carried out by varying the concentration, pH and temperature. Sorption of the 2,4-D and MCPA unto the biochar were fitted to two- and three-parameter isotherm models. The adsorption capacities were ∼134 mg/g and ∼50 mg/g for 2, 4-D and MCPA, respectively. Unexpectedly, low surface area switchgrass biochar was found to remove more 2,4-D and MCPA per unit of measured surface area (45 mg/m2) than high surface area commercial activated carbons ( 0.08–0.11 mg/m2). Our results show the potential application of the fast pyrolysis switchgrass biochar to remove wastewater contaminated with phenoxy herbicides.