Tunable production of elemental Se vs. H₂Se through photocatalytic reduction of selenate in synthetic mine impacted brine: engineering a recoverable Se product

Abstract

In this paper, we investigate the tunability of selenium reduction products (Se0(s) vs. H2Se(g)) during the photocatalytic reduction of selenate over TiO2, using formic acid as an electron hole scavenger,...

Photocatalytic nanoparticles in flow-through annular photoreactors for continuous selenate reduction in industrial wastewater

“…Then, Se 0 (s) may be further reduced to gaseous H 2 Se (g) by electrons at the Se 0 (s) conduction band ( e − CB,Se ) or by CO 2 ˙ − radicals formed through the oxidation of formic acid (eqn (5)). 30,31,44 SeO 4 2− + 8H + + 6 e − CB,TiO2 → Se 0 (s) + 4H 2 OSe 0 (s) + 2H + + 2 e − CB,Se (2CO 2 ˙ − ) → H 2 Se (g) (+2CO 2(g) )From the BBD experimental results (Table S2†), ANOVA was performed to calculate the parameter estimates, t -values, and p -values for each term of the model. The results of the analysis for both precent Se reduction and E EO,UV models are presented in Table S3 †…”

“…SMIB was synthesized following a procedure from previously reported work. 30 In brief, as-received MIW was spiked with additional NaNO 3 , NaCl, CaSO 4 , and Na 2 SeO 4 to match target brine concentrations of 518 mg L −1 NO 3 − (as N), 2070 mg L −1 SO 4 2− , 3570 μg L −1 SeO 4 2− (as Se), and 60 mg L −1 Cl − . Next, the pH of the SMIB was increased to 11 using Ca(OH) 2 and gently stirred overnight.…”

“…SMIB was synthesized following a procedure from previously reported work. 30 In brief, as-received MIW was spiked with additional NaNO 3 , NaCl, CaSO 4 , and Na 2 SeO 4 to match target brine concentrations of 518 mg L −1 NO 3 − (as N), efficiency), an air-tight effluent tank (1 L capacity), and two chemical scrubbers for gas handling (500 mL of 0.01 M CuSO 4 and 0.1 M NaOH, respectively). The experimental setup is illustrated in Fig.…”

“…Then, Se 0 (s) may be further reduced to gaseous H 2 Se (g) by electrons at the Se 0 (s) conduction band (e − CB,Se ) or by CO 2 ˙− radicals formed through the oxidation of formic acid (eqn (5)). 30,31,44 Environmental Science: Nano Paper…”

“…28,29 Photocatalysis has only recently been demonstrated to selectively remove Se from complex industrial wastewaters and brine matrices in the presence of characteristically elevated sulfate and nitrate levels. 30,31 Furthermore, these recent studies elucidate the effect of matrix constituents and photocatalytic reaction conditions on Se photoreduction kinetics, including the inhibitory effect of sulfate, 31 and the typical Arrhenius temperature-rate constant relationship. 30 As a result, through optimized conditions, TiO 2 photocatalysis can reduce Se oxyanions in the presence of common co-contaminants, yields recoverable H 2 Se and solid elemental Se as reduction products, and produces minimal waste if the photocatalysts can be recovered and re-used.…”