Pyrolysis of chemically treated corncob for biochar production and its application in Cr(VI) removal

Abstract

In this study, corncob was used as raw material for biochar production. Slow pyrolysis of corncob was done at different temperatures (400–600°C) with a constant heating rate of 16°C/min in a quartz reactor with the aim to produce biochar. The physicochemical treatment of corncob was done to make it suitable for pyrolysis. Chemical treatment was done at different o-phosphoric acid to corncob ratio (PA/CC) of 0.5, 1.0 and 1.2 for improvement of quality and yield of produced biochar. With increasing temperature biochar yield decreased but pretreatment showed an increase in the yield. Biochar yield was found optimum at PA/CC of 1.0. The FTIR, SEM, TGA and XRF analysis of corncob and biochar were done to see the changes before and after pyrolysis. Presence of different inorganic elements along with lesser H/C and O/C ratios makes biochar as additive for soil amendment. Also lesser H/C and O/C ratios and HHV of 19.97 MJ/kg confirms biochar suitable as solid fuel. Further application of biochar was examined for Cr(VI) removal from aqueous solution as innovative adsorbent in batch process with varying parameters such as pH, initial concentration of Cr(VI) solution, contact time and adsorbent dose. Maximum removal of Cr(VI) was found to be 93% at pH 2.01, initial Cr(VI) concentration 50 mg/L, adsorbent dose 10 g/L and equilibrium time of 90 min. Langmuir isotherm showed a better fitting model and maximum adsorption capacity was 25.69 mg/g. Biochar showed good repeatability by reusing it twice as adsorbent for Cr(VI) removal. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1606–1617, 2018. © 2017 American Institute of Chemical Engineers