Characterization and evaluation of biochars derived from agricultural waste biomasses from Gansu,China

Abstract

Five biochars derived from cotton (Gossypium herbaceum) straw, cotton residue, potato (Solanum tuberosum) straw, potato residue and swine (Sus scrofa domesticus) manure, termed as BCCS, BCCR, BCPS, BCPR and BCSM, were characterized and evaluated. SEM micrographs showed that BCs had recognizable pore size which also contributed to their higher surface areas except BCSM450. XRD patterns showed peaks found at 2θ at d=3.35 A and d=3.16-3.00 A were related to quartz (SiO2) and calcite (CaCO3), respectively, while these peaks were non-recognizable in BCCS as a result of their amorphous nature. Proximate analysis showed that the highest moisture content in BCCR (9.65%) whereas BCSM recorded the highest ash content (15.22%). The elemental analysis showed that carbon content increased from 58.97 to 81.28%. Atomic ratios, polarity index and aromatic ratios also showed remarkable results. Surface areas for BCCR, BCCS, BCPR, BCPS and BCSM were 126.08, 443.96, 15.43, 30.84, and 67.88 m/g, respectively. The cationic exchange capacities (CEC) (48.26, 77.30, 34, 59.48 and 71.83 cmolc/kg for BCCR, BCCS, BCPR, BCPS and BCSM), were determined, respectively. Boehm titration indicated that BCCS (8.85 mmol/g) and BCPR (2.25 mmole/g) showed the highest and lowest acidities. FTIR spectrum appears to be quite different for BCs. Common bands around 3600 and 1078 cm were assigned to polymeric hydroxyl (ROH) and carbonyl esters (C=O), respectively. The results demonstrated the potential of BC as an amendment to adsorb and immobilize heavy metals in loess soil.