Methylene blue adsorption on Parinari excelsa biochar in aqueous solution

Methylene blue (MB) dye, similar to many modern dyes, poses environmental problems. Parinari excelsa is a large tropical tree that is common in many parts of humid Africa and tropical South America. In this study, biochar prepared from P. excelsa wood waste was characterized. Batch stud-ies were conducted to determine the MB adsorption efficiency of the P. excelsa biochar. The MB adsorption efficiency increased with increasing the contact time, biochar dosage, pH and sodium chloride concentration. Also the percentage uptake decreased with increasing the initial concen-tration of MB solution. The adsorption equilibrium data were fitted with Langmuir, Freundlich, Temkin and D-R isotherm models. The analysis showed that the Langmuir model showed the best isotherm fit, while the adsorption kinetics was best described by pseudo-second-order kinetic model. The adsorption mechanism was described as physisorption. The adsorption capacity of 30 mg/g was estimated and the equilibrium was obtained within 720 min by removing 97% of MB from the aqueous solution. This research confirmed that P. excelsa biochar would serve as an effective adsorbent for the uptake of MB in aqueous solution.