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

Zhe Yang,Bin Yao,Avelino Núñez-Delgado,Liangchen Shen,Feifeng Jiang,Wenyong Hu,Yaoyu Zhou

doi:10.3390/pr9071209

Abstract

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.

Highlights

Environmental pollution caused by heavy metals or their compounds is mainly driven by mining and dressing, electroplating, smelting, and a variety of uses of heavy metal products [1,2]
According to the analysis of the infrared spectroscopy, we found that the increase in the pyrolysis temperature caused some characteristic peaks of the biochars to shift or disappear, and it should be noted that the presence of abundant surface functional groups can improve the capacity of the manganese-rich pokeweed biochars as regards adsorption of the heavy metal ions [38]
The H/C ratio of the BC300, BC400, and BC500 materials constantly diminished, which indicates that the increase in the pyrolysis temperature could promote the carbonization of the biochars and contribute to a higher aromaticity

Summary

Introduction

Environmental pollution caused by heavy metals or their compounds is mainly driven by mining and dressing, electroplating, smelting, and a variety of uses of heavy metal products [1,2]. Pb) present in the left lands around the manganese ore area enter the surrounding water (surface water and groundwater), or reach soil, resulting from washing and dissolution by rainwater. These facts suppose high risks of damaging the safety of agriculture and animal husbandry production, as well as for human and environmental health [6,7]. Pb, and Cd are the most common heavy metals presenting toxicity Once they enter the human body via drinking, eating, breathing or via direct contact, they will deposit and accumulate, with high risks of causing significant damage to the normal function of the body [8,9]. It could produce teratosis or induce cancer [10,11]

Methods

Results

Conclusion