Lead removal from aqueous solutions using biochars derived from corn stover, orange peel, and pistachio shell
2019
Mireles, S. | Parsons, John | Trad, T. | Cheng, C.-L. | Kang, J.
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.
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