Abstract
AbstractCr(III) adsorption from textile industrial effluent was studied with the aim of contributing towards achieving targets of SDG 6 (Sustainable Development Goals). Highly toxic effluent discharge from textile industries cause the majority of the pollution of waterways which is due to the unaffordability of the existing effluent treatment techniques. Proven efficiency of modified sawdust to adsorb heavy metals could be a sustainable solution as an abundantly available industrial byproduct of sawdust. Biochar derived from sawdust by pyrolizing at 400 °C was further modified using 0.1M KOH or 0.1M H2O2 solutions separately. Batch experiments conducted using synthetic Cr(III) aqueous solution in neutral pH condition indicated an equilibrium contact time of 1 h with optimum initial Cr(III) concentration of 5 mg/L with 1 and 2 g of adsorbent dosages for KOH and H2O2 modified biochars respectively under single solute system. Further competitive Cr(III) adsorption with the presence of Cu(II) and Zn(II) were examined through batch studies. Results indicated that Cr(III) adsorption was favored in pH base range when examined under multi-metal system along with Cu(II) and Zn(II). Adsorption capacities were increased with the physical and chemical modifications. The physical characterization carried out using Specific Surface Area (SSA) analysis showed a 97.9% increase of SSA when raw sawdust was modified into biochar. KOH and H2O2 modifications had further increased the SSA of biochar by 37.8% and 51.5% respectively. X-ray Powder Diffraction (XRD) analysis confirmed the removal of impurities in adsorbents after physical and chemical modifications while the Point of Zero Charge (pHpzc) analysis established the favorability of using a neutral pH in the solution media. Heavy metal removal percentages were observed as 97.5 and 94.1% for KOH modified biochar and H2O2 modified biochar under optimum conditions. Findings suggest that the higher SSA and stability of the added functional groups lead the KOH modification to sawdust derived biochar to be an efficient, environmental friendly adsorbent which could be used in treatment of heavy metals in industrial effluent. Further chemical characterizations using SEM and FTIR analyses could be recommended to evaluate the surface properties of the adsorbents.KeywordsAdsorptionSawdustBiocharPhysical and chemical modificationHeavy metal
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