Fixation of carbon dioxide and optimization of liming process waste produced in tanneries using response surface methodology

Abstract Tanning process generates a significant amount of waste matter both in solid and liquid form. The present study depicts an innovative approach to reduce pollutant and recover calcite (CaCO 3 ) from the liming process waste by carbon dioxide (CO 2 ) fixation. Response surface optimization was applied to study the effect of time and lime concentration (2.5%–7.5% w/w) in synthetic wastewater using CO 2 . The acquired optimized condition was verified on real solid waste produced viz., lime sludge product (LSP) and relime sludge product (RSP). The results indicated rover >95% of calcite (CaCO 3 ) recovery from synthetic lime wastewater followed by 85–90% from LSP & RSP under optimized conditions. Subsequent reduction of total dissolved solids and suspended solids in the range of 78–82% and 76–77% in LSP & RSP was also observed. Mineralogical analysis using X-ray diffraction technique along with standards (lime, calcite, lime & calcite mix) confirms the production of calcite. Statistical analysis showed a P value  2  > 0.95) among the process conditions and variables using response surface methodology and was further validated using artificial neural networking. This study demonstrates a sustainable and cleaner way of resource recovery from waste through CO 2 fixation from lime solid waste (sludge).