Removal Efficiency of Heavy Metals Such as Lead and Cadmium by Different Substrates in Constructed Wetlands

Abstract

In order to find an efficient and economical wetland substrate to treat mine wastewater containing various heavy metals, and effectively realize the resource utilization of water treatment residuals, in this paper, the treatment efficiency of mine wastewater containing various heavy metals was investigated using unburned ceramsite prepared from water treatment residuals (UCWTR) and clay ceramsite. The continuous dynamic test results showed that the removal rate of Pb, Cd, Cu, Zn, and Fe can reach more than 98.5% after the UCWTR-based CWs runs for 56 days, and its concentration was 30.05%, 24.85%, 20.82%, 14.63%, and 7.91% lower than that of the clay ceramsite-based CWs, respectively. SEM, XPS, and FT-IR showed that the characteristic peaks of two ceramsites were basically similar. The ceramsite undergoes ion exchange, coordination complexation, and chelation reaction with Pb, Cd, Cu, Zn, and Fe under the action of the gel of internal groups -OH, C=O, Al-OH, Si-Fe-O and C-S-H. Compared with clay ceramsite, the ion exchange reaction and chelation reaction of -OH effect and the coordination reaction of C=O effect of carboxyl group in UCWTR were enhanced. In conclusion, using UCWTR as a CWs substrate can effectively enhance the adsorption capacity of heavy metals, providing a scientific basis for the application of UCWTR-based CWs in mine wastewater treatment.

A Critical Review of Green Approach on Wastewater Treatment Strategies

“…Limited pollutant removal: Constructed wetlands are effective at removing certain pollutants such as organic matter and nutrients but may not be as effective at removing other pollutants such as heavy metals and some chemicals (Fu et al, 2022;Inobeme et al, 2022).…”

Comparative evaluation of different substrates compiled in column‐type vertical‐flow constructed wetlands to remove heavy metals

“…Differences in substrate type largely affect the integrated functions of CWs, including the physical, chemical, and biological functions, which determine their overall HM removal efficiency and sustainability. Nevertheless, comparisons of the effectiveness of different substrates for HM removal under the same experimental settings are limited (Chen et al., 2009; Fu et al., 2022; Lizama Allende et al., 2012). In addition, although previous studies have successfully confirmed the excellent ability of various substrates to remove HMs from wastewater, most studies focused on relatively low HM concentrations (<10 mg/L) (A et al., 2017; Chen et al., 2021; Zhao et al., 2020) and studies on the effective removal of higher concentrations of HMs, which are likely encountered in the treatment of industrial wastewater and leachate, by CWs with short hydraulic retention time (HRT) are still scared.…”