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 (CaCO3) from the liming process waste by carbon dioxide (CO2) 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 CO2. 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 (CaCO3) 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 < 0.05 indicating a higher degree of correlation (R2 > 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 CO2 fixation from lime solid waste (sludge).