Investigation of Modified Biochar Performance on Nitrate Removal from Aqueous Solution: Kinetic and Isotherm Study

Biochar modification is performed to improve the structure of pores, increase the specific surface area, functional groups, and reduction of raw biochar limits in absorption of pollutants. This study was conducted to evaluate the efficiency of corn stover modified biochar in adsorption of nitrate from aqueous solution. For this purpose, corn stover biochar (BC) and chemically modified corn stover biochar with MgCl2 (Mg-BC) was prepared at 500°C and its physico-chemical characteristics were measured. Adsorption batch experiments were carried. Effects of initial concentration of nitrate, contact time and pH on adsorption capacity mechanism were studied. The study of the characteristics of the two types of biochar showed that by the chemical modification of corn stover, enhanced yields, pH, surface area, cation exchange capacity and anion exchange capacity, oxygen content, H/C and O/C ratio, while decreased carbon content and C/N ratio. Adsorption of nitrate by both biochar reached to equilibrium after 480. The optimal pH for removal of nitrate was 3. The results demonstrated that chemical modification of biochar enhanced nitrate adsorption and maximum nitrate adoption by BC and Mg-BC was 51.72 and 72.18, respectively. Langmuir isotherm showed the best fit for nitrate in both biochars. The pseudo second order kinetic model also provided a good description for the adsorption process nitrate.Generally, result of present study revealed that modification of biochar could improve physico-chemical and adsorption capacity of nitrate from aqueous solution. Therefore, MgCl2 modified biochar could be a suitable absorbent for purifying water resources which contaminated by inorganic pollutants, including nitrate.