Removal of Chloride Ions from Strongly Acidic Wastewater Using Cu(0)/Cu(II): Efficiency Enhancement by UV Irradiation and the Mechanism for Chloride Ions Removal

Abstract

Strongly acidic wastewater, which is usually generated from nonferrous metal smelting industries, has the ability to be recycled as sulfuric acid. Before this wastewater is recycled, the removal of chloride ions is necessary to improve the quality of the recycled sulfuric acid. At present, the widely used method to remove chloride ions from acidic wastewater in the form of CuCl precipitate has several disadvantages, including low removal efficiency, high temperature, long treatment time, and high dosage of Cu(II). This study proposed an improved new method of removing Cl(−I) using Cu(0)/Cu(II) under UV irradiation, and the mechanism was investigated. The Cl(−I) concentration was lowered to below 50 mg/L at a Cu(II) dosage of 1200 mg/L. Under UV irradiation, ligand-to-metal charge transfer takes place, thereby resulting in the formation of Cl • . Next, CuCl precipitates form through the reaction between Cu(0) and Cl • and produce h + / • OH under UV irradiation, which can oxidize Cl(−I) to Cl • . Simultaneously, Cl 2 gas also forms directly from Cl • . This study offered a theoretical foundation for the application of UV irradiation for the enhanced removal of chloride ions from strongly acidic wastewater.

UV-Improved Removal of Chloride Ions from Strongly Acidic Wastewater Using Bi2O3: Efficiency Enhancement and Mechanisms

“…(a) UV–vis absorption spectra and plot of A ( hv ) versus energy ( hv ) for the band gap energy of Bi 2 O 3 and BiOCl. (b) VB-XPS spectra of Bi 2 O 3 and BiOCl.…”

“…ESR results show that • OH was indeed generated in the treatment (Figure S6). However, Cl • , which should also be produced in the reaction solution containing a large quantity of Cl − , 2,25,31 was not detected probably because of its high conversion rate. Under UV irradiation, h + can oxidize OH − and Cl − to • OH and Cl • , respectively.…”

“…Currently, neutralization using lime or limestone, the most common method to treat this kind of wastewater, has a major problem of producing massive CaSO 4 waste containing heavy metals. − Therefore, recycling this kind of wastewater as diluted sulfuric acid after the contaminants being removed was proposed to avoid producing large amounts of CaSO 4 waste. − The technology to remove As and heavy metal ions using a sulfuration method has attracted considerable attention in recent years, and high efficiency can be achieved. , Among the contaminants contained in this kind of wastewater, Cl – , the concentration of which can be up to thousands or even tens of thousands parts per million, is rather difficult to remove. In our previous study, we proposed to remove Cl – from acidic wastewater under ultraviolet (UV) irradiation using Cu 2+ /Cu 0 as the precipitant, and high Cl – removal efficiency was achieved . To further lower the cost of this method, employing copper slag, a kind of byproduct from nonferrous metal smelting industries, instead of Cu 0 powder was also suggested.…”

“…In our previous study, we proposed to remove Cl − from acidic wastewater under ultraviolet (UV) irradiation using Cu 2+ /Cu 0 as the precipitant, and high Cl − removal efficiency was achieved. 2 To further lower the cost of this method, employing copper slag, a kind of byproduct from nonferrous metal smelting industries, instead of Cu 0 powder was also suggested. Therefore, this method is generally applicable in the enterprises that produce copper slag as a byproduct, in consideration of the high cost of Cu 0 powder.…”

Heterostructured α-Bi2O3/BiOCl Nanosheet for Photocatalytic Applications

“…The high Cl − content could cause metal corrosion, soil salinization and human diseases. The conventional removal technique of Cl − in acidic wastewater is to use Cu(0) and Cu(II) for generating CuCl precipitate [ 29 ]. Unfortunately, the low removal efficiency (<60%) would lead to a high concentration of residual Cl − (>400 mg/L).…”