Lead removal from aqueous solutions using biochars derived from corn stover, orange peel, and pistachio shell
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Biochar has been viewed as a cost-effective adsorptive material for heavy metals in water. In the present study, a total of nine different biochars synthesized from three different biomass types were studied: corn stover, organic peel, and pistachio shell at three pyrolysis temperatures (300, 450, and 600 °C). The efficiency of lead ion (Pb2+) removal by the biochars was investigated through batch adsorption experiments in parallel with physicochemical characterization of the biochars. Single-point Pb2+ adsorption at 10 mg L−1 showed that high-temperature corn stover biochar at 600 °C and low-temperature orange peel biochar at 300 °C performed the best in the Pb2+ removal (> 94%). Pistachio shell biochars were relatively poor at removing aqueous Pb2+ (20–35%). The efficiency of the Pb2+ removal increased with increasing pH (2–6) until a maximum adsorption of Pb2+ was observed at pH 6. Adsorption isotherms for Pb2+ were conducted using the best-performing biochars per biomass based on the single-point adsorption results. All isotherms were best described by the Langmuir model, and the Pb2+ sorption capacities were 25,000 mg kg−1 for corn stover biochar at 600 °C, 11,111 mg kg−1 for orange peel biochar at 300 °C, and 2500 mg kg−1 for pistachio shell at 600 °C. The physicochemical properties of biochars indicated that oxygen-containing functional groups and specific surface area were major parameters affecting aqueous Pb2+ removal. This study highlights that biomass type and pyrolysis temperature as well as solution pH are important in affecting the adsorption efficiency of Pb2+ from aqueous solution.
KeywordsBiochar Lead Adsorption isotherm Pyrolysis Fourier transform infrared spectroscopy
Funding was provided by faculty startup for Kang and a graduate assistantship from the University of Texas Rio Grand Valley. We like to thank Thomas Eubanks for his help with SEM–EDX analyses. We also thank anonymous reviewers for their valuable comments and suggestions on the manuscript.
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