Efficient removal of Cr(VI) from aqueous solution by hydrochloric acid and polypyrrole co-modified sludge-based biochar

Abstract

In this work, in view of the poor adsorption capacity of sludge-based biochar, a sludge-based biochar adsorbent co-modified with hydrochloric acid and polypyrrole (PPy/SBC-HCl) was prepared and used to remove Cr(VI) from aqueous solution. Its characterization of SEM, EDS, BET, XRD, FT-IR, and XPS show that the removal mechanism of Cr(VI) by PPy/SBC-HCl includes electrostatic adsorption, ion exchange, reduction, and complexation. The removal efficiency of Cr(VI) by PPy/SBC-HCl decreases with the increase of pH. The coexisting cations Ca²⁺ and Mg²⁺ have a slight negative effect on it, while the oxoacid anions have a great negative effect on it. The adsorption of Cr(VI) by PPy/SBC-HCl is a spontaneous endothermic process, which conforms to the pseudo-second-order adsorption kinetic model and the Freundlich adsorption isotherm model. The maximum adsorption capacity is 97.37 mg g⁻¹ at pH 2.0 and temperature 298 K.

GRAPHICAL ABSTRACT

Keywords:

• Sludge-based biochar
• PPy
• HCl
• Cr(VI)
• adsorption

Disclosure statement

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, “Efficient removal of Cr(VI) from aqueous solution by hydrochloric acid and polypyrrole co-modified sludge-based biochar”.

Additional information

Funding

Financial support from the National Natural Science Foundation of China (No. 52176178, 51876018), Innovation Research Group of Universities in Chongqing (No. CXQT21035), Scientific and Technological Research Program of Chongqing Municipal Education Commission of China (No. KJZD-M202201101), and Action Plan for High Quality Development of Graduate Education of Chongqing University of Technology (Grant gzltd202204) are gratefully acknowledged.