Adsorption of Methylene Blue Using Biochar, soil and Treated Soil with Biochar from aqueous solutions

Industrial dyes are one of the largest organic compounds with potential application in different industries. According to their complex aromatic structure and that they are man-made, they are stable compounds and their purification is difficult . Sewage containing dyestuffs causes surface and sub-surface water pollution and also causes soil contamination through irrigation. If these effluents enter the environment without purification, they can impose irreparable damage to the environment. Therefore, it is necessary to reclaim wastewaters and contaminated soil by using effective methods. Among the suitable methods for removing dyes, adsorption is one of the best and most appropriate techniques for dye removal. In this study, the effect of rice straw biochar (RSB) which is produced at 600˚C, soil and mixture of soil and biochar on methylene blue adsorption from aqueous environments was investigated. First, rice straw was turned to biochar at 600˚C. Then biochar was mixed with sandy soil which was taken from alluvial plains of Tajan area of Sari, Mazandaran province at ratios 1, 2.5 and 5 (w/w). Methylene blue dye solution was prepared from methylene blue powder, and 40 mL of solution with concentrations of 30-300 mg/L and pH=7 was added to 0.1 g biochar, soil and mixture of soil and biochar and finally, methylene blue sorption isotherms were determined for biochar, soil and mixture of soil and biochar. Experiments were performed in a completely randomized design with three replications. The results of fitting the data obtained from the Langmuir and Freundlich isotherm model showed that methylene blue adsorption on the RSB produced at 600 ° C, soil and mixture of soil and biochar matches with the Langmuir isotherm model and the langmuir model fitted well with the absorption process. biochar, mixture of biochar and soil and soil treatments had the maximum adsorption capacities with amounts of 27.85, 3.272 and 17.953 mg/g, respectively. Due to biochar high specific surface area, high cation exchange capacity and the presence of functional groups, it had a high adsorption of methylene blue. In general, the results showed that methylene blue adsorption isotherms by the biochar, soil and mixture of soil and biochar were L-shaped and there was a fairly high desire for absorption. Results also showed that incorporation of biochar to soil enhanced the adsorption capacity of soil, thus it can be concluded that RSB could improve methylene blue adsorption in soil environment.