Removal of hexavalent chromium (Cr(VI)) from aqueous solution using acid‐modified poultry litter‐derived hydrochar: adsorption, regeneration and reuse

Abstract

BACKGROUND: Chromium (Cr) is widely used in industrial processes and is considered a major source of pollution when released to the environment. Of particular concern, hexavalent chromium (Cr(VI)) is amongst the most toxic heavy metals affecting human health and living organisms when fugitive emissions contaminate aqueous environments. Consequently, its removal and recovery are priorities for environmental remediation in the context of the circular economy. In this study, modified hydrochar (MHC) was generated by hydrothermal carbonisation of acid-treated (H 2 SO 4 ) poultry litter (PL) and investigated for its ability to adsorb Cr(VI) from aqueous solution in batch studies. Recovery of Cr(VI) and the regeneration potential of MHC were also evaluated.RESULTS: Results indicated that Cr(VI) adsorption was strongly pH dependent, demonstrating an inverse relationship between solution pH and Cr(VI) uptake. A maximum adsorption capacity of 26.2 mg g −1 was achieved in 90 min at pH 2. Under optimal conditions, adsorption kinetics followed a pseudo-second-order kinetic model and the adsorption isotherm fitted most closely with the Langmuir model. Thermodynamic studies indicated that the adsorption process of Cr(VI) onto the MHC was exothermic and spontaneous. Regeneration studies demonstrated that the MHC can be re-used up to four times without significant loss of capacity to adsorb Cr(VI).CONCLUSIONS: Modified PL hydrochar offers potential as a low-cost, environmentally friendly solution for Cr(VI) adsorption in wastewater treatment applications. The ability of Cr(VI) to desorb from MHC demonstrates strong potential for Cr(VI) recovery and regeneration of the adsorbent.

Efficient removal of anionic dye by protonated APTES modified hydrochar: The effect of cold‐activation

“…However, it is not a very effective adsorbent for especially anionic pollutants due to its rich oxygencontaining functional groups. Hence, to enhance their adsorption performances, the surface can be easily activated (acidic or basic) or modified due to its abundant oxygen-containing functional groups [20,21]. NaOH or KOH-activated HC has been widely utilized and the surface of HC has been modified with diverse functional groups for the removal of generally cationic pollutants [22][23][24].…”

Inversion of loading‐implicit adsorption isotherms by means of the Lambert W function

“…Commonly used isotherm models include the equations of Langmuir, Freundlich, Sips, and Dubinin-Radushkevich. [1][2][3] Many software packages, including Excel, 4 offer standard nonlinear regression methods to fit these isotherm equations to experimental data. The conventional nonlinear regression procedure minimizes the sum of squared residuals (SSR) using a fitting algorithm.…”

“…Experimentally measured isotherms for water contaminant adsorption on solid materials are generally correlated using suitable theoretical or empirical models. Commonly used isotherm models include the equations of Langmuir, Freundlich, Sips, and Dubinin—Radushkevich 1‐3 . Many software packages, including Excel, 4 offer standard nonlinear regression methods to fit these isotherm equations to experimental data.…”

Removal of Cr(VI) by a simply prepared biochar‐supported nanoscale zero‐valent iron

“…Cr(VI) is highly migratory and toxic, which is higher than Cr(III). 3,4 Long-term exposure to Cr(VI) is likely to cause cancer, teratogenesis and mutagenicity. 5 Therefore, the removal of Cr(VI) in polluted wastewater is the key to ensure the safety of water quality, which has attracted increasing attention in recent years.…”

“…Chromium mainly exists in the form of Cr(VI) and Cr(III). Cr(VI) is highly migratory and toxic, which is higher than Cr(III) 3,4 . Long‐term exposure to Cr(VI) is likely to cause cancer, teratogenesis and mutagenicity 5 .…”