Abstract
Here, a dual-modification strategy using KMnO4 (potassium permanganate) and AlCl3·6H2O (aluminum chloride, hexahydrate) as co-modifiers to improve the Cr(VI) removal capacity of K2CO3 activated biochar is introduced. As a result, the dual-modified biochar with KMnO4 and AlCl3·6H2O has the calculated adsorption energy of −0.52 eV and −1.64 eV for HCrO4−, and −0.21 eV and −2.01 eV for Cr2O72−. The Al2O3 (aluminum oxide) and MnO (manganese oxide) embedded on the surface of dual-modified biochar bring more Cr(VI) absorption sites comparing to single-modified biochar, resulting in a maximum Cr(VI) saturated adsorption capacity of 152.86 mg g−1. The excellent removal performance is due to the synthetic effect of electrostatic attraction, reduction reaction, complexation reaction, and physical adsorption. The experimental results also indicated that the spontaneous adsorption process agreed well with the pseudo-second order and Langmuir models. This dual-modification strategy is not limited to the treatment of Cr(VI) with biochar, and may also be incorporated with the treatment of other heavy metals in aqueous environment.
Highlights
Discharge of chromium-containing wastewater has led to destruction of the aquatic ecological environment
The results showed that the maximum adsorption capacity of biochar and modified biochar for Cr(VI) were 37.17 mg g−1 and 67.88 mg g−1, respectively [9]
Many adsorbents, such as biochar [10], metal oxide nanoparticles [11], and graphene [12] have been explored for heavy metal removal
Summary
Discharge of chromium-containing wastewater has led to destruction of the aquatic ecological environment. Effective methods are needed to remove Cr(VI) in wastewater to protect the aquatic environment and human health Various methods, such as adsorption [3], chemical precipitation [4], ion exchange [5], and electrochemical techniques [6] have been applied to remove heavy metals. The results showed that the maximum adsorption capacity of biochar and modified biochar for Cr(VI) were 37.17 mg g−1 and 67.88 mg g−1, respectively [9] Many adsorbents, such as biochar [10], metal oxide nanoparticles [11], and graphene [12] have been explored for heavy metal removal. While many methods focused on the improvement of adsorption capacity via single modification, the impact of dual-modifiers on the removal performance of biochar still needs to be explored. The dual-modified biochar (AMKBC) showed a significant improvement of physicochemical properties and Cr(VI) removal capacity compared to the single-modified biochar
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