Mechanism, Adsorption kinetics and applications of carbonaceous adsorbents derived from black liquor sludge

Abstract

Pretreatment processes in second generation bioethanol production produce a lignin-based black liquor. Polyaluminum chloride (PACl) was employed to treat black liquor using coagulation, in which the generated sludge was converted to a carbonaceous adsorbent. The bioethanol black liquor sludge-based carbonaceous adsorbent (BBLS-CA) was characterized physically, and its adsorption mechanism, kinetics, and ability to absorb methylene blue (MB) were evaluated. Additional studies revealed the performance of BBLS-CA to treat peat water and landfill leachate. The results demonstrate that BBLS-CA decolorized a 100 mg/l solution of MB by 98% within 30 min. MB components reclaimed from BBLS-CA reveal the presence of NH2, substituted and p-disubstituted benzene rings, and =CH2, suggesting that physical and chemical mechanisms are operative during adsorption. Isotherm analysis reveals that adsorption equilibrium followed the Langmuir model and exhibited pseudo second-order kinetic behavior. BBLS-CA adsorbed 100% iron and manganese; and remediated 72% color and 67% COD in peat water, as well as 57% COD in landfill leachate. This report highlights a by-product from black liquor sludge that can be applied to the removal of wastewater pollutants. Further, the development of method is required to obtain activated carbon which fulfills standard properties of activated carbon.