Adsorption of Malachite Green and Pb2+ by KMnO4-Modified Biochar: Insights and Mechanisms

Wei Wang,Hua Deng,Weixing Gan,Mianwu Meng,Lening Hu,Junyu Zhang,Rui Huang

doi:10.3390/su14042040

Abstract

In this study, the feasibility and mechanism of Pb2+ and malachite green (MG) adsorption from wastewater using KMnO4-modified bamboo biochar (KBC) was evaluated. The KBC was characterized by SEM–EDS, XRD, FTIR and XPS. The adsorption results for Pb2+ conformed to pseudo-second-order kinetics and the Langmuir model theory. Unlike the case for Pb2+, the Freundlich model better described the adsorption behaviour of MG, indicating that adsorption occurred within multiple molecular layers. Both pseudo-first-order kinetics and pseudo-second-order kinetics fit the MG adsorption data well, indicating that physical adsorption was involved in the adsorption process. In addition, the maximum adsorption capacity for Pb2+/MG was 123.47/1111.11 mg·g−1, KBC had high adsorption capacities for Pb2+ and MG, and the mechanisms of Pb2+ adsorption were mineral precipitation, functional group complexation, and cation-π interactions, while the main mechanisms for MG adsorption were pore filling, π–π interactions, and functional group complexation. In this study, KMnO4-modified biochar was prepared and used as an efficient adsorbent, and showed good application prospects for treatment of wastewater containing MG and Pb2+.

Highlights

With the rapid development of industrial and agricultural modernization, pollution from heavy metals and organic wastewater has become increasingly serious [1]
In the pH 2–3 range, the adsorption of malachite green (MG) by KMnO4-modified bamboo biochar (KBC) increased from 252.73 mg·g−1 to 366.38 mg·g−1, which may be because the solution pH was less than pHPZC = 7.76 (Figure 1a); there were positive charges on the surface of KBC, strong electrostatic repulsions between MG and KBC, and the solution contained a high H+ concentration and a high capacity for protonation [31], resulting in poor adsorption
The results showed that the R2 values of the cated that adsorption of MG and Pb by KBC proceeded differently

Summary

Introduction

With the rapid development of industrial and agricultural modernization, pollution from heavy metals and organic wastewater has become increasingly serious [1]. Malachite Green is a common dye and a controversial antibacterial agent used in aquaculture which acts on the immune system and reproductive system of the human body, causing irreversible damage to human health [3]. These two types of wastewater pose serious threats to the ecological environment as well as to human survival and development. Common wastewater treatment methods include electroflocculation [4], ion exchange [5], and membrane separation [6] These methods often have disadvantages, such as high application costs, long treatment cycles, and low efficiencies. In comparing the adsorption performance of banana straw and cassava

Objectives

Methods

Results

Conclusion