Recovery of Cr(III) by using chars from the co-gasification of agriculture and forestry wastes

Godinho, D, Nogueira M, Bernardo M, Dias D, Lapa N, Fonseca I, Pinto F.  2019.  Recovery of Cr(III) by using chars from the co-gasification of agriculture and forestry wastes, Aug. Environmental Science and Pollution Research. 26:22723–22735., Number 22


The aim of the present work was to assess the efficiency of biochars obtained from the co-gasification of blends of rice huskþinspace}+þinspace}corn cob (biochar 50CC) and rice huskþinspace}+þinspace}eucalyptus stumps (biochar 50ES), as potential renewable low-cost adsorbents for Cr(III) recovery from wastewaters. The two gasification biochars presented a weak porous structure (ABETþinspace}=þinspace}63–144 m2 g−1), but a strong alkaline character, promoted by a high content of mineral matter (59.8{%} w/w of ashes for 50CC biochar and 81.9{%} w/w for 50ES biochar). The biochars were used for Cr(III) recovery from synthetic solutions by varying the initial pH value (3, 4, and 5), liquid/solid (L/S) ratio (100–500 mL g−1), contact time (1–120 h), and initial Cr(III) concentration (10–150 mg L−1). High Cr(III) removal percentages (around 100{%}) were obtained for both biochars, due to Cr precipitation, at low L/S ratios (100 and 200 mL g−1), for the initial pH 5 and initial Cr concentration of 50 mg L−1. Under the experimental conditions in which other removal mechanisms rather than precipitation occurred, a higher removal percentage (49.9{%}) and the highest uptake capacity (6.87 mg g−1) were registered for 50CC biochar. In the equilibrium, 50ES biochar presented a Cr(III) removal percentage of 27{%} with a maximum uptake capacity of 2.58 mg g−1. The better performance on Cr(III) recovery for the biochar 50CC was attributed to its better textural properties, as well as its higher cation exchange capacity.



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