Aims: Biochar produced from different waste biomass has been documented as an adsorbent for heavy metal removal from contaminated water. In present study, Banana peduncle which considered as waste, but abundantly available and have high biomass was selected for production of biochar to investigate its adsorption capacity for hexavalent chromium. Place and Duration of Study: Environment and Sustainability Department, CSIR-Institute of Minerals and Materials Technology (CSIR-IMMT), Bhubaneswar, India, between April 2014 and October 2014. Methodology: Banana peduncle pyrolysed at 300°C and 500°C temperature and characterized by proximate, total carbon, FE-SEM, FTIR and XPS analysis. The adsorption of Cr (VI) studied through the batch experiment at different pH, adsorbent dose, and initial concentration. Results: The banana peduncle biochar yield was 66 and 40% at 300°C and 500°C respectively. The Cr (VI) removal and adsorption capacity of biochar was found to be dependent on pH, initial chromium concentration, and biochar dose. Maximum Cr (VI) removal of 91.18 and 54.06% was obtained at pH-2, 50 mg/l initial concentration and 2 g/l biochar adsorbent dose for BC-300 and BC-500 respectively. The regression co-efficient values show that adsorption of Cr (VI) fitted well with Langmuir and Freundlich isotherm. However, relatively higher Cr (VI) monolayer adsorption capacity (114 mg/g) was found in biochar produced at 300°C than 500°C (49 mg/g). The FE-SEM, FTIR, and XPS analysis indicates adsorption coupled reduction of Cr (VI) to Cr (III) and complexation of Cr (III) with hydroxyl and carboxyl group of biochar are responsible for its removal. Conclusion: The research findings reflect about the suitability of banana peduncle’s biochar for Cr (VI) adsorption from polluted waste water.

Hansenula polymorpha is a non-conventional and thermo-tolerant yeast that is well-known for its use in the industrial production of recombinant proteins. However, research to evaluate this yeast’s potential for the high-temperature fermentation of sugar to produce alcohols for biofuel applications is limited. The present work investigated a wild-type H. polymorpha strain (DSM 70277) for the production of ethanol at a temperature of 40 °C under limited oxygen presence by using a batch fermentation reactor. Fermentation experiments were performed using three types of sugar (glucose, fructose, xylose) as substrates with two initial inoculum concentrations (1.1 g·L⁻¹ and 5.0 g·L⁻¹). The maximum specific growth rates of H. polymorpha yeast were 0.121–0.159 h⁻¹ for fructose, 0.140–0.175 h⁻¹ for glucose, and 0.003–0.009 h⁻¹ for xylose. The biomass volumetric productivity was 0.270–0.473 g·L⁻¹h⁻¹ (fructose), 0.185–0.483 g·L⁻¹h⁻¹ (glucose), and 0.001–0.069 g·L⁻¹h⁻¹ (xylose). The overall yield of ethanol from glucose (0.470 g·g⁻¹) was higher than that from fructose (0.434 g·g⁻¹) and xylose (0.071 g·g⁻¹). The H. polymorpha yeast exhibited different behavior and efficacy regarding the use of glucose, fructose, and xylose as substrates for producing ethanol. The present knowledge could be applied to improve the fermentation process for valorization of waste biomass to produce bioethanol.