Potentials of surface modified biochar for removal of Cr from tannery effluent and its regeneration to ensure circular economy

AbstractIndustries play a substantial role in contaminating the freshwater sources. This study was performed to appraise the potential of biochar activated with 85% phosphoric acid was used as chemisorbent for the removal of Chromium III and VI (Cr III and VI)) and desorbed chromium was utilized for replacing the conventional basic chromium sulfate to ensure circular economy. In our previous studies, the factors for biosorption of Cr were optimized through Box–Behnken model under Response Surface Methodology. Batch adsorption studies revealed that the optimum conditions for maximum Cr (VI) biosorption by activated biochar is pH = 2, biosorbent dose: 1%, biosorbent size: 1 mm, solute concentration: 985 mg L−1 and reaction time 35 h. Based on these results a column experiments were carried out and flow rate was optimized as 0.5 ml m−1 where prominent “S” shaped breakthrough curves were noticed. The predicted values under Thomas model for the adsorption of Cr was 3827.2 µg g−1, which was in close agreement with experimental value of 3566.1 µg g−1. The percent Cr sorption varied from 70.05 to 88.75% in first cycle and showed decreasing trend in the subsequent cycles. The elutant 0.5 M H2SO4 desorbed 89.56% of chromium furthermore eluted chromium was utilized for leather tanning. Reusing of recovered chromium for tanning experiments does not alter the leather Tensile (240.82 kg cm−2) and tear strengths (32.41 kg mm−1). This study suggested that recovered chromium from biosorbent can be well utilized for leather tanning to attain the leather of equivalent qualities as that of conventional methods which could save 20–22% of the production cost besides defending the environment from Cr contamination.Keywords: Activated biocharadsorptionbiosorbentchromiumdesorptiontannery effluenttanning AcknowledgmentsThe authors are grateful to the anonymous reviewers and editors for their insightful comments that helped us sufficiently improve the quality of the article.Author informationDepartment of Environmental Sciences, Tamil Nadu Agricultural Universitytry, Coimbatore, India Ettiyagounder Parameswari, Rajakumaran Kalaiarasi, Veeraswamy Davamani, Periyasamy Kalaiselvi, and Selvaraj Paulsebastian.Department of Vegetable Science, Tamil Nadu Agricultural Chemistry, Coimbatore, IndiaTamilselvan IlakiyaContributionsConceptualization: Ettiyagounder Parameswari; Methodology: Periyasamy KalaiselviFormal analysis and investigation: Rajakumaran KalaiarasiWriting original draft preparation: Veeraswamy Davamani; Tamilselvan Ilakiya;Review and editing: Selvaraj Paul Sebastian;Funding acquisition: Ettiyagounder Parameswari;Resources and Supervision: Veeraswamy Davamani; Tamilselvan IlakiyaCorresponding author: Correspondence to Ettiyagounder ParameswariDisclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe authors thank the Science and Engineering Research Board (YSS/2015/001432), Department of Science and Technology, New Delhi for financial assistance.