Doping a metal (Ag, Al, Mn, Ni and Zn) on TiO₂ nanotubes and its effect on Rhodamine B photocatalytic oxidation

Xinghua Gao,Beihai Zhou,Rongfang Yuan 대한환경공학회 2015 Environmental Engineering Research Vol.20 No.4

The effects of ion-doping on TiO₂ nanotubes were investigated to obtain the optimal catalyst for the effective decomposition of Rhodamine B (RB) through UV photocatalytic oxidation process. Changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the BET surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on RB removal increased when Ag(+), Al^³⁺ and Zn²⁺ were doped into the TiO₂ nanotubes, whereas such activities decreased as a result of Mn²⁺ or Ni²⁺ doping. In the presence of Zn²⁺-doped TiO₂ nanotubes calcined at 550℃, the removal efficiency of RB within 50 min was 98.7%.

Isolation of bacteria capable of removing 2-methylisoborneol and effect of cometabolism carbon on biodegradation

Kang Du,Jian Liu,Beihai Zhou,Rongfang Yuan 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.3

2-Methylisoborneol (2-MIB) is one of typical odorants in potable water sources, which is hardly removed by conventional water treatment process. In this study, three strains capable of removing 2-MIB singly from drinking water were isolated from activated carbon of sand filter. They were identified to be Shinella zoogloeoides, Bacillus idriensis and Chitinophagaceae bacterium based on 16S rRNA gene sequence analysis. In mineral salts medium without external carbon source, removal efficiencies of 20 μg/L 2-MIB in three days were 23.3%, 32.9% and 17.0% for Shinella zoogloeoides, Bacillus idriensis and Chitinophagaceae bacterium, respectively. The biodegradation of 2-MIB was significantly improved with the presence of cometabolism carbon(glycerol, glucose, etc.). In the period of 20 days, Bacillus idriensis can remove 2 mg/L MIB to 368.2 μg/L and 315.4μg/L in mineral salts medium without and with glycerol respectively. The removal of 2-MIB by Bacillus idriensis was from 2 mg/L to 958.4μg/L in Xiba river samples on 15 days.

Enhanced photocatalytic oxidation of humic acids using Fe<SUP>3+</SUP>-Zn<SUP>2+</SUP> co-doped TiO₂

Rongfang Yuan,Dan Liu,Shaona Wang,Beihai Zhou,Fangshu Ma 대한환경공학회 2018 Environmental Engineering Research Vol.23 No.2

Photocatalytic oxidation in the presence of Fe-doped, Zn-doped or Fe-Zn co-doped TiO₂ was used to effectively decompose humic acids(HAs) in water. The highest HAs removal efficiency (65.7%) was achieved in the presence of 500°C calcined 0.0010% Fe-Zn co-doped TiO₂ with the Fe:Zn ratio of 3:2. The initial solution pH value, inorganic cations and anions also affected the catalyst photocatalytic ability. The HAs removal for the initial pH of 2 was the highest, and for the pH of 6 was the lowest. The photocatalytic oxidation of HAs was enhanced with the increase of the Ca<SUP>2+</SUP> or Mg2+ concentration, and reduced when concentrations of some anions increased. The inhibition order of the anions on TiO₂ photocatalytic activities was CO₃<SUP>2-</SUP> > HCO₃<SUP>-</SUP> > Cl-, but a slightly promotion was achieved when SO₄<SUP>2-</SUP> was added. Total organic carbon (TOC) removal was used to evaluate the actual HAs mineralization degree caused by the 500°C calcined 0.0010% Fe-Zn (3:2) co-doped TiO₂. For tap water added with HAs, the UV254 and TOC removal rates were 57.2% and 49.9%, respectively. The UV254 removal efficiency was higher than that of TOC because of the generation of intermediates that could significantly reduce the UV254, but not the TOC.

The mechanisms of conventional pollutants adsorption by modified granular steel slag

Shaona Wang,Sijian Yao,Kang Du,Rongfang Yuan,Huilun Chen,Fei Wang,Beihai Zhou 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.1

This study was performed to investigate the removal of phosphorus, nitrogen, ammonia and dissolved organic matter (DOM) from domestic wastewater using modified granular steel slag (GSS) as adsorbent. The modification methods include acid modification, alkalinity modification and thermal modification. The GSS modified at 800°C for 1 h was easier to hydrolyze Ca<SUP>2+</SUP>, which could promote the precipitation of phosphates and the ion exchange process of ammonia. Therefore, the adsorptive capacity of GSS for phosphates and ammonia could be significantly improved by the thermal treatment. The acid-modified GSS promoted the adsorption capacity of nitrates by increasing surface protonation, specific surface area and pore size. The highest nitrates adsorption capacity was obtained when GSS was immersed in 1 mol/L HCl solution for 24 h. The presence of nitrates inhibited the adsorption of phosphates by GSS because the adsorption of nitrates and phosphates by GSS depended largely on electrostatic attraction and intermolecular force, and the competition between them reduced the adsorption capacity. Ammonia can promote the hydrolysis of metal ions on the surface of GSS, increase the concentration of metal ions in solution and promote the formation of phosphate precipitation, but ammonia also competed with phosphate for active sites on the surface of GSS. The effect of ammonia nitrogen on phosphate adsorption was the result of the interaction of the two mechanisms. For domestic wastewater, the thermally modified GSS showed the best adsorption rate of total phosphorus and total nitrogen, and the acid-modified GSS had better adsorption capacity for organic matter. The thermally modified GSS had a good application effect in laboratory subsurface flow constructed wetlands.

Effects of sulfonamide antibiotics on digestion performance and microbial community during swine manure anaerobic digestion

Shaona Wang,Kang Du,Rongfang Yuan,Huilun Chen,Fei Wang,Beihai Zhou 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.1

The effects of four types of sulfonamide antibiotics (SAs), including sulfaquinoxaline, sulfamethoxazole, sulfamethoxydiazine and sulfathiazole, on the digestion performance during anaerobic digestion process were studied using a lab-scale anaerobic sequencing batch reactor, and the changes of the community structure in the presence of SAs were investigated with the help of high throughput sequencing. The results indicated that when SAs were added, the hydrolytic acidification process was inhibited, and the accumulation of volatile fatty acids (VFAs) was induced, resulting in the suppression of methane production. However, the inhibition mechanism of different SAs was quite different. The inhibitory effect of high concentration of SAs on the hydrolysis of solid particulate matter into dissolved organic matter followed the order of sulfaquinoxaline > sulfamethoxydiazine > sulfathiazole > sulfamethoxazole. SAs have obvious inhibitory effects on acidification and methanation of dissolved organic matter, especially sulfathiazole. The richness and the community composition of the microorganism including bacteria and archaea in the digestion system were affected by SAs. Under the effect of SAs, the relative abundance of many microorganisms is negatively correlated with methane production, among which Methanobrevibacter, a kind of Archaea, had the greatest influence on methane production.

Adsorption of phosphate by Mg/Fe-doped wheat straw biochars optimized using response surface methodology: Mechanisms and application in domestic sewage

Hao Wang,Jiangyue Dai,Huilun Chen,Fei Wang,Yangchen Zhu,Jia Liu,Beihai Zhou,Rongfang Yuan 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.2

In this study, Mg/Fe-doped biochar (MFDB) was prepared using the impregnation pyrolysis method, and its preparation was optimized using response surface methodology (RSM). The competitive adsorption between dissolved organic matter (DOM) and phosphorus was also investigated. The best adsorption capacity was obtained with an ㎎ impregnation ratio of 3.17:1 (Mg: biomass, g:g), Fe impregnation ratio of 1.3:1 (Fe: biomass, g:g), and pyrolysis temperature of 491℃. The adsorption capacity of MFDB for phosphorus was 179.21 ㎎/g at 40℃, an initial phosphate concentration of 50 ㎎/g and pH 4. The phosphate adsorption by MFDB conformed to a pseudo-primary and secondary adsorption kinetic model, proving the coexistence of physical and chemical adsorption. The adsorption mechanisms, including ligand exchange, electrostatic interaction, and complexation reaction were revealed. As the pH increased, it weakened the electrostatic interaction of phosphate by MFDB and the ligand exchange between phosphate and OH⁻. When the pH was less than 3, the metal oxide dissolved. For pH values exceeding, OH⁻ competed with phosphate for adsorptio, which also weakened the complexation of phosphate and MFDB. The DOM in domestic wastewater had a slight effect on the phosphorus adsorption. The phosphorus removal rates were closely related to lignin-like humic acid and tryptophan.