Abstract
Nano-zero-valent iron biochar derived from almond shell (nZVI-ASBC) was used for hexavalent chromium (CR) removal. Experiments showed that pH was the main factor (p < 0.01) that affected the experimental results. At a dosage of 10 mg·L−1 and pH of 2–6, in the first 60 min, nZVI-ASBC exhibited a removal efficiency of 99.8%, which was approximately 20% higher than the removal yield at pH 7–11. Fourier transform infrared spectroscopy results indicated N-H was the main functional group that influenced the chemisorption process. The pseudo second-order dynamics and Langmuir isotherm models proved to be the most suitable. Thermodynamic studies showed that the reaction was exothermic and spontaneous at low temperatures (T < 317 K). Various interaction mechanisms, including adsorption and reduction, were adopted for the removal of Cr(VI) using the nZVI-ASBC composite. The findings showed that the BC-modified nZVI prepared with almond shell exerts a good effect and could be used for the removal of Cr(VI).
Highlights
As industrialization proceeds, water pollution continues to elicit much attention
Qian et al [15] found BC synthesized from corn stalk could be used as a carrier of nano-zero-valent iron (nZVI) and to reduce agglomeration, which showed that metals can be removed by this modified nZVI
The process lasted for about an hour. nZVI-ASBC was eventually separated using a vacuum suction bottle, washed with alcohol, dried, and stored in a sealed bag filled with N2 to avoid oxidation
Summary
Water pollution continues to elicit much attention. Hexavalent chromium [Cr(VI)] is a typical toxic heavy metal contaminant produced mainly from industrial processes, such as steel fabrication, metal processing, tanning, dyeing, leather, and paint manufacturing [1]. NZVI has a large specific surface area and small particle size, which prove to be beneficial for removing heavy metals [8,9]. Qian et al [15] found BC synthesized from corn stalk could be used as a carrier of nZVI and to reduce agglomeration, which showed that metals can be removed by this modified nZVI. We used BC made from almond shells as the carrier of nZVI. Almond shells are directly discarded as garbage This waste was collected and processed to create valuable BC, which was used as a carrier for nZVI to prepare nZVI loaded on almond BC (nZVI-ASBC). We analyzed the mechanism of Cr removal by nZVI-ASBC in detail. Fourier transform infrared spectroscopy (FTIR) was implemented to analyze the functional groups that attached to the surface of BC before and after the reaction
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