Abstract
Removal of aquatic cadmium ions using biochar is a low-cost method, but the results are usually not satisfactory. Modified biochar, which can be a low-cost and efficient material, is urgently required for Cd-polluted water and soil remediation. Herein, poplar bark (SB) and poplar sawdust (MB) were used as raw materials to prepare modified biochar, which is rich in N- and S- containing groups, i.e., TSBC-600 and TMBC-600, using a co-pyrolysis method with thiourea. The adsorption characteristics of Cd2+ in simulated wastewater were explored. The results indicated that the modification optimized the surface structure of biochar, Cd2+ adsorption process by both TSBC-600 and TMBC-600 was mainly influenced by the initial pH, biochar dosage, and contact time, sthe TSBC-600 showed a higher adsorption capacity compared to TMBC-600 under different conditions. The Langmuir adsorption isotherm model and pseudo-second-order kinetic model were more consistent with the adsorption behavior of TSBC-600 and TMBC-600 to Cd2+, the maximum adsorption capacity of TSBC-600 and TMBC-600 calculated by the Langmuir adsorption isotherm model was 19.998 mg/g and 9.631 mg/g, respectively. The modification method for introducing N and S into biochar by the co-pyrolysis of biomass and thiourea enhanced the removal rate of aquatic cadmium ions by biochar.
Highlights
Cadmium (Cd) has extreme biological toxicity, long half-life, and low elimination efficiency [1]
An N, S modified biochar was prepared by the co-pyrolysis of thiourea and poplar bark (SB) or poplar sawdust (MB), and used for the removal of aquatic cadmium ions
The results showed that the performance of thiourea-modified biochar was stable
Summary
Cadmium (Cd) has extreme biological toxicity, long half-life, and low elimination efficiency [1]. It is one of the “ten chemicals of major public health concern” listed by the World Health Organization [2]. In 2014, the fraction of points that exceeded the standard quantity of Cd in cultivated land in China was 7% [4], and the area of farmland polluted by Cd reached 20 million hectares, which was mainly caused by irrigation due to industrial wastewater [5]. The methods for the removal of Cd2+ in wastewater are mainly chemical precipitation, ion exchange, membrane separation, coagulation, and adsorption [9]. Biochar is a type of carbon-rich porous material [10], which is accessible by high-temperature conversion of biomass
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