A Novel Manganese-Rich Pokeweed Biochar for Highly Efficient Adsorption of Heavy Metals from Wastewater: Performance, Mechanisms, and Potential Risk Analysis

• Main Authors: Zhe Yang, Wenyong Hu, Bin Yao, Liangchen Shen, Feifeng Jiang, Yaoyu Zhou, Avelino Núñez-Delgado
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Processes
• Subjects: biochar; heavy metal; adsorption; performance; mechanisms; potential risk analysis
• Online Access: https://www.mdpi.com/2227-9717/9/7/1209

A novel manganese-rich pokeweed biochar was prepared at different temperatures from manganese-rich pokeweed plants collected at manganese tailings, resulting in materials identified as BC300, BC400, and BC500. The synthetized biochar materials were investigated as regards their potential for removing Cu²⁺, Pb²⁺, and Cd²⁺, specifically in terms of adsorption performances, adsorption kinetics, adsorption isotherms, and potential environmental pollution risk. The results showed that the sorption process fitted well to the pseudo-second-order kinetic and Langmuir models, and the maximum adsorption capacities of BC500 were 246, 326, and 310 mg·g⁻¹ for Cu²⁺, Pb²⁺, and Cd²⁺ respectively. The physicochemical characteristics of the biochars, and the adsorption mechanisms, were revealed by using scanning electron microscopy-energy spectrometer, elemental analysis, Brunauer–Emmett–Teller techniques, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The sorption mechanism of these three heavy metal ions onto biochars included ion exchange, electrostatic adsorption, chemical adsorption, and precipitation. Besides, the potential pollution risk of manganese-rich pokeweed biochars was significantly reduced after pyrolysis. Therefore, it is feasible to transform manganese-rich pokeweed biomass into manganese-rich pokeweed biochar with potential for heavy metals removal, showing high adsorption capacity, recyclability, and low environmental pollution.