Kinetics of Cu, Pb and Zn removal during soil flushing with washing agents derived from sewage sludge

Barbara Klik,Dorota Kulikowska,Zygmunt M Gusiatin

doi:10.1038/s41598-021-89458-z

Barbara Klik, Dorota Kulikowska + Show 1 more

Open Access

https://doi.org/10.1038/s41598-021-89458-z

Copy DOI

Journal: Scientific Reports	Publication Date: May 12, 2021
Citations: 2	License type: open-access

Affiliation: University of Warmia and Mazury in Olsztyn

Abstract

This paper presents the first tests of Cu (7875 mg/kg), Pb (1414 mg/kg) and Zn (566 mg/kg) removal from contaminated soil with sewage-sludge–derived washing agents (SS_WAs) (dissolved organic matter, DOM; soluble humic-like substances, HLS; soluble humic substances, SHS) and Na2EDTA (as a standard benchmark) in column experiments. Flow rates of 0.5 ml/min and 1 ml/min were used. Using a 1. order kinetic model, the kinetic constant (k), the maximum concentrations of each metal removed (Cmax), and the initial rates of metal removal (r) were established. At both flow rates, stable flow velocity was maintained for approximately eight pore volumes, for flushing times of 8 h (1.0 ml/min) and 16 h (0.5 ml/min). Although the flow rate did not influence k, it influenced Cmax: at 1 ml/min, Cmax values were higher than at 0.5 ml/min. For Cu and Zn, but not Pb, k was about twofold higher with Na2EDTA than with SS_WAs. Although Na2EDTA gave the highest kCu, Cmax,Cu was highest with DOM (Na2EDTA, 66%; DOM 73%). For Pb removal, HLS was the most effective SS_WA (77%; Na2EDTA was 80% effective). kZn was about twofold higher with Na2EDTA than with SS_WAs. Cmax,Zn was highest with HLS. The quick mobilization of Cu, Pb and Zn with most of the WAs corresponded to efficient metal removal from the exchangeable (F1) fraction.

Highlights

This paper presents the first tests of Cu (7875 mg/kg), Pb (1414 mg/kg) and Zn (566 mg/kg) removal from contaminated soil with sewage-sludge–derived washing agents (SS_WAs) and Na2EDTA in column experiments
Based on cumulative heavy metals (HMs) removal, kinetic constants were calculated, according the 1. order kinetic formula: C = Cmax · 1 − e−k·t where: Cmax is the maximum concentration of the individual HMs (Cu, Pb, Zn) removed from washed soil; k is the kinetic constant of the individual HM removal ( h−1); t is the soil flushing time (h)
The soil in the column reactor was flushed with more pore volumes during a shorter flushing time at the higher flow rate than at the lower rate

Summary

Introduction

This paper presents the first tests of Cu (7875 mg/kg), Pb (1414 mg/kg) and Zn (566 mg/kg) removal from contaminated soil with sewage-sludge–derived washing agents (SS_WAs) (dissolved organic matter, DOM; soluble humic-like substances, HLS; soluble humic substances, SHS) and Na2EDTA (as a standard benchmark) in column experiments. Order kinetic model, the kinetic constant (k), the maximum concentrations of each metal removed (Cmax), and the initial rates of metal removal (r) were established At both flow rates, stable flow velocity was maintained for approximately eight pore volumes, for flushing times of 8 h (1.0 ml/ min) and 16 h (0.5 ml/min). The spent washing agent is recovered, reused, and eventually treated and disposed of This technology is applicable to homogenous, coarse-textured soils with high permeability, and its main advantages are the elimination of the need to excavate, handle, and transport large quantities of contaminated soil, and its relatively small surface footprint, which allows it to be used in space-limited a reas[15]. Yang et al.[19] used bench-scale column washing to examine the efficiency of removal of DTPA-extractable HMs (Cd, 12.82 mg/kg; Pb, 105.38 mg/kg) using different doses of HCl and N a2EDTA in a contaminated calcareous soil.

Methods

Results

Conclusion