Heavy metal recovery from electroplating effluent using adsorption by jute waste-derived biochar for soil amendment and plant micro-fertilizer.

Effluent from electroplating industries contains various toxic heavy metal ions such as chromium, nickel, lead, cadmium, copper and zinc. Recovery of the valuable heavy metals by environment friendly approach for recycling in various useful applications could be significant from the perspectives of clean process development with techno-economic viability. Zinc is an important component of electroplating effluent found in high concentration (80–750 mg/L). The present study investigates on recovery of zinc from electroplating effluent using an efficient biochar synthesized from jute industrial wastes. Biochar characteristics and metal removal mechanisms were established using BET surface area, zeta potential, FESEM-EDAX, elemental mapping, XRD, FTIR, XPS, XRF, Raman spectroscopy and roles played by functional groups. Optimum adsorption capacity of 526.32 mg g⁻¹ was obtained for Zn(II). Zn(II) binding was achieved by ion exchange, complexation with functional groups, electrostatic interactions, adsorption and micro-precipitation. The techno-economic analysis was performed for biochar prepared by chemical carbonization process and found competitive in comparison with other reported biochar obtained by slow pyrolysis process. Further, the disposal of the toxic metal-laden spent adsorbent is a critical issue that needs to be addressed. In the present study recycling potential of the exhausted Zn(II)-laden biochar was explored for the development of micro-fertilizer for plants and soil-fertility improvement. Application of the Zn(II)-laden biochar mixed with soil revealed a positive influence on Cicer arietinum seed germination, plant growth parameters, protein and chlorophyll a and b content. Significantly, there were no changes in the antioxidant enzymes activities, superoxide dismutase (SOD) and catalase (CAT) between the plants grown in control soil and different Zn(II)-laden biochar-mixed soil, suggesting that 15% of the Zn(II)-laden biochar could not be excess condition of zinc. The present study thus addresses an important aspect of solid waste management of jute industry considering significant volume of jute waste production of ~ 0.04 MT/day in India along with the remediation of electroplating and other metal-bearing industrial effluent. Further, micro-fertilizer application of the metal-laden sludge and soil productivity improvement at low cost, environmentally safe and fruitful manner makes the study significant from ecological as well as societal perspectives. [ABSTRACT FROM AUTHOR]