Reduction behavior of chromium(VI) with oxalic acid in aqueous solution

Abstract

The direct Cr(VI) reduction process by oxalic acid was conducted. The existence of Cr(VI) in the reaction medium was measured by software Visual MINTEQ and the concentration of Cr(VI) was measured by ICP-OES. The results showed that the Cr(VI) was efficiently reduced by oxalic acid at high reaction temperature and high dosage of oxalic acid. The reduced product, Cr(III), was easily generated stable complex compounds (Cr(HC2O4)3) with oxalate, which displayed a negative effect on the reduction process. The high reaction temperature and high acidic medium could destroy the stable structure of a complex compound to release oxalate, and facilitate the reduction of Cr(VI). Generally, the results showed in this paper provided a versatile strategy for Cr(VI) reduction and exhibited a bright application future for real wastewater treatment.

Efficient Removal of Cr (VI) with Biochar and Optimized Parameters by Response Surface Methodology

“…The analysis of variance of the reduction efficiency of Cr (VI) is shown in Table 2. The results show that the p-value of the model was <0.0001, which indicates that the selected model was significant and suitable for simulating the reduction process of Cr (VI) [21,30]…”

“…A recent study indicated that Cr (VI) is easily reduced to Cr (III) in a strong acidic medium [12,13,21]. A series of experiments were conducted with the concentration of H 2 SO 4 ranging from 0 to 20 g/L at various dosages of biochar.…”

“…After a required reaction time, the solution with Cr (III) and retained biochar were separated by vacuum filtration. The concentration of Cr (VI) in the filtrate was determined by titration with ferrous ammonium sulfate [12,13,21], and the reduction efficiency (η) of Cr (VI) was calculated following Equation (1):…”

“…In this paper, the pseudo-first-order model-as described as Equation ( 3)-was applied to simulate the reduction behavior of Cr (VI) [12,21,33,34].…”

“…Therefore, it is urgent to develop useful technologies for Cr (VI) treatment [16][17][18]. Recently, the reduction of Cr (VI) to Cr (III) has attracted much more attention [12,13,[19][20][21]. The reduction process of Cr (VI) with oxalic acid with and without Mn (II) has been investigated and the results showed that Cr (VI) could not be reduced in an oxalic acid solution or an Mn (II) solution, while nearly 99% of Cr (VI) reduced to Cr (III) in an oxalic acid solution mixed with Mn (II).…”