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Assessing the efficiency and mechanism of zinc adsorption onto biochars from poultry litter and softwood feedstocks
Citation:
O'Connor, K., Souhail R. Al-Abed, S. Hordern, AND P. Pinto. Assessing the efficiency and mechanism of zinc adsorption onto biochars from poultry litter and softwood feedstocks. Bioresource Technology Reports. Elsevier B.V., Amsterdam, Netherlands, 18:101039, (2022). https://doi.org/10.1016/j.biteb.2022.101039
Impact/Purpose:
Biochar is a relatively cheap, commercially available, and efficient method of heavy metal remediation in aquatic systems. However, due to biochar being created from a myriad of different biomass sources, it is important to understand the adsorption mechanisms of metals onto biochars in order to efficiently implement this technique in the field. The objective of this study was to assess the removal of zinc in aqueous solution using four biochars from multiple biomass residues (poultry litter and three tree species). Additionally, the mechanisms behind metal removal was explored using batch and kinetic experiments. All four of the biochars used in this experiment showed significant removal of zinc from solution using both DI water and a natural river water as matrices. We determined that the optimal pH for zinc adsorption for all four biochars was 10 using pH batch experiments. Significant zinc removal happened within the first 4 hours of biochar addition and should be used to inform future applications of these biochars in the field. Results from various isotherm models determined the mechanism of zinc adsorption onto the different biochars was best fit using the Langmuir model, suggesting a monolayer adsorption onto the biochar surface. Relative contributions between adsorption mechanisms differed between ligneous and poultry litter biochar; however, cation exchange with minerals, precipitation, and surface complexation and coordination with π electrons were the dominant mechanism in all biochars. XRD and XPS results further validated the removal of zinc from aqueous solution by adsorption. Knowledge of these biochars can assist in aqueous zinc treatments at a myriad of sites, including at the Tar Creek Superfund site, where zinc contamination is of great concern. By knowing the mechanisms of adsorption associated with these biochars, engineers can design and implement short- and long-term remediation efforts.
Description:
The efficiency and adsorption mechanism of zinc removal was assessed in aqueous solution using four biochars from multiple biomass residues (poultry litter and three tree species). The effect of pH, kinetic effects, and isotherm fittings were investigated, as well as zinc-laden biochar using x-ray diffraction and absorption near edge structure. Sorbent load results showed softwood biochar exhibited the greatest zinc removal from both deionized (15 mgZn/L) and mining influenced river water (10 mgZn/L). The Langmuir isotherm was the best fit for the majority of the biochars. Exchangeable cations contributed most for the adsorption mechanism from the softwood biochars, while precipitation was greatest contribution for the poultry litter biochar. Overall, our results suggest that biochars from Douglas Fir trees are more efficient at removing zinc from aqueous solutions (up to 19.80 mgZn/g) compared to previously studied biochars (0.61 to 11.0 mgZn/g) and should be used for future remediation efforts.
URLs/Downloads:
DOI: Assessing the efficiency and mechanism of zinc adsorption onto biochars from poultry litter and softwood feedstocks
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