Vermicompost as a natural adsorbent: evaluation of simultaneous metals (Pb, Cd) and tetracycline adsorption by sewage sludge-derived vermicompost

Abstract

The simultaneous adsorption of heavy metals (Pb, Cd) and organic pollutant (tetracycline (TC)) by a sewage sludge-derived vermicompost was investigated. The maximal adsorption capacity for Pb, Cd, and TC in a single adsorptive system calculated from Langmuir equation was 12.80, 85.20, and 42.94 mg L⁻¹, while for mixed substances, the adsorption amount was 2.99, 13.46, and 20.89 mg L⁻¹, respectively. The adsorption kinetics fitted well to the pseudo-second-order model, implying chemical interaction between adsorbates and functional groups, such as –COOH, –OH, –NH, and –CO, as well as the formation of organo-metal complexes. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) specific surface area measurement were adopted to gain insight into the structural changes and a better understanding of the adsorption mechanism. The sewage sludge-derived vermicompost can be a low cost and environmental benign eco-material for high efficient wastewater remediation.

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