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

Enhanced Decolorization and Treatment of Textile Dye Wastewater Through Adsorption on Acid Modified Corncob Derived Biochar

“…This happens because the molecules found in the solid biochar are broken down at higher temperatures in pyrolysis to create smaller molecules that enrich the liquid and gaseous products thus resulting in reduced biochar yield. The comparable pattern of reduction in biochar yield was similar as observed in a previous study by Gupta et al [20] …”

“…Proximate analysis of corncob revealed the moisture content (5.0 %), volatile matter (69.9 %), fixed carbon (15.9 %) and ash content (9.2 %). The fixed carbon and volatile matter present in corncob could be used for the production of biochar and bio‐oil respectively [20] . The ratio of volatile matter to fixed carbon was 4.39.…”

“…The H/C and O/C ratio for BC was 0.48 and 0.178. Gupta et al [20] . reported a longer life cycle of over 1000 years for biochar having O/C ratio <0.2 and found it appropriate for carbon sequestration and soil amendment.…”

“…For removal of dyes which are persistent after this treatment, advanced techniques like chemical oxidation or adsorption are required as majority of these dyes are non‐biodegradable [13–15] . So, to advance a conservative arrangement, development of eco‐friendly and cost‐effective adsorbents has gained high importance as the expenses are much lower in comparison to the other advanced methods including ion exchange, membrane filtration, ozonation, photochemical oxidation, sonolysis, and so forth [16–22] …”

Efficiency of biochars in the removal of heavy metals

“…Other biomasses are also being used for the removal of chromium in aqueous environment, such as Saccharum officinarum L. (sugarcane) (Ferreira et al, 2015;Ferreira, 2018); Elaeis guineensis (African palm) (Tejada-Tovar et al, 2015); Dioscorea spp. (yam) (Tejada-Tovar et al, 2015); Juglans regia L. (walnut shells) (Altun & Kar, 2016); Zea mays (corn) (Gupta, Ram, Bala, Kapur, & Mondal, 2018); Oryza sativa (rice) (Miguel, 2017). The adsorption capacity of these biocarbons ranged from 0.2884 to 41.57 mg g -1 , corresponding to removal efficiencies of 29.13 to 99.97%.…”