Photopolymerization of Coating Materials for Protection against Carbon Steel Corrosion.

This work demonstrated a workable approach for the synthesis of a re-healing polyaniline-modified epoxy resin coating material via photopolymerization. The prepared coating material exhibited low water absorption, allowing it to be used as an anti-corrosion protective layer for carbon steel. First, graphene oxide (GO) was synthesized through the modified Hummers' method. It was then mixed with TiO2 to extend its light response range. The structural features of the coating material were identified using scanning electron microscopy (SEM), X ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT IR). The corrosion behavior of the coatings and the pure resin layer were tested by using electrochemical impedance spectroscopy (EIS) and the potentiodynamic polarization curve (Tafel). The presence of TiO2 reduced the corrosion potential (Ecorr) toward lower values in 3.5% NaCl at room temperature, which was due to the photocathode of titanium dioxide. The experimental results indicated that GO was successfully compounded with TiO2 and that GO effectively improved the light utilization capacity of TiO2. The experiments showed that the presence of local impurities or defects can reduce the band gap energy, resulting in a lower Eg for the 2GO:1TiO2 composite (2.95 eV) compared to that of TiO2 alone (3.37 eV). After applying visible light to the coating surface, the change in the Ecorr value of the V-composite coating was 993 mV and the value of Icorr decreased to 1.993 × 10-6 A/cm2. The calculated results showed that the protection efficiency of the D-composite and V-composite coatings on composite substrates was approximately 73.5 and 83.3%, respectively. More analyses revealed that under visible light, the coating had better corrosion resistance. This coating material is expected to be a candidate for carbon steel corrosion protection.

Design an Epoxy Coating with TiO2/GO/PANI Nanocomposites for Enhancing Corrosion Resistance of Q235 Carbon Steel.

In this work, a ternary TiO2/Graphene oxide/Polyaniline (TiO2/GO/PANI) nanocomposite was synthesized by in situ oxidation and use as a filler on epoxy resin (TiO2/GO/PANI/EP), a bifunctional in situ protective coating has been developed and reinforced the Q235 carbon steel protection against corrosion. The structure and optical properties of the obtained composites are characterized by XRD, FTIR, and UV-vis. Compared to bare TiO2 and bare Q235, the TiO2/GO/PANI/EP coating exhibited prominent photoelectrochemical properties, such as the photocurrent density increased 0.06 A/cm2 and the corrosion potential shifted from -651 mV to -851 mV, respectively. The results show that the TiO2/GO/PANI nanocomposite has an extended light absorption range and the effective separation of electron-hole pairs improves the photoelectrochemical performance, and also provides cathodic protection to Q235 steel under dark conditions. The TiO2/GO/PANI/EP coating can isolate the Q235 steel from the external corrosive environment, and may generally be regarded a useful protective barrier coating to metallic materials. When the TiO2/GO/PANI composite is dispersed in the EP, the compactness of the coating is improved and the protective barrier effect is enhanced.

Groundwater arsenic removal using granular TiO2: integrated laboratory and field study.

High concentrations of arsenic (As) in groundwater pose a great threat to human health. The motivation of this study was to provide a practical solution for As-safe water in As geogenic areas using granular TiO2 (GTiO2). The kinetics results indicated that the As (III/V) adsorption on GTiO2 conformed to the Weber-Morris (WM) intraparticle diffusion model. The Langmuir isotherm results suggested that the adsorption capacities for As (III) and As (V) were 106.4 and 38.3 mg/g, respectively. Ion effect study showed that cationic Ca and Mg substantially enhanced As (V) adsorption, whereas no significant impact was observed on As (III). Silicate substantially decreased As (V) adsorption by 57 % and As (III) by 50 %. HCO3 (-) remarkably inhibited As (V) adsorption by 52 %, whereas it slightly reduced As (III) adsorption by 8 %. Field column results demonstrated that ∼700 µg/L As was removed at an empty bed contact time (EBCT) of 1.08 min for 968 bed volumes before effluent As concentration exceeded 10 µg/L, corresponding to 0.96 mg As/g GTiO2. Two household filters loaded with 110 g GTiO2 in the on-off operational mode can provide 6-L/day As-safe drinking water up to 288 and 600 days from the groundwater containing ∼700 µg/L As and ∼217 µg/L As, respectively. Integration of batch experiments and column tests with systematic variation of EBCTs was successfully achieved using PHREEQC incorporating a charge distribution multisite complexation (CD-MUSIC) model and one-dimensional reactive transport block.

Evaluation of chromium bioaccessibility in chromite ore processing residue using in vitro gastrointestinal method.

Incidental ingestion of Chromite ore processing residue (COPR) particles poses a potential health risk. The purpose of this study was to determine the Cr bioaccessibility from COPR using the in vitro gastrointestinal (IVG) procedure. The bioaccessible Cr(VI) was 53.8% and 42.9%, respectively, in the gastric and intestinal phases from a total of 19490 mg kg(-1) Cr(VI) in COPR. Food intake including milk, dough, and ascorbic acid resulted in a significant decrease in Cr(VI) bioaccessibility. Some organic acids such as lactic, malic, and citric acid moderately reduced Cr(VI), while acetic acid exhibited no capacity for Cr(VI) reduction. The integrated area under the concentration-time curve (AUC) of the IVG extraction was used to calculate bioaccessibility. Compared with the bioaccessibility conventionally estimated using concentrations at the end of the extraction (CEP), the AUC technique should be implemented to confirm the accuracy of the IVG method when reduction of Cr(VI) occurs during the extraction. The absence of Cr(VI) phases in extracted residues as evidenced by XANES and XRPD analysis confirmed the Cr(VI) release and Cr(VI) reduction by food and ascorbic acid. With readily bioaccessible Cr(VI) and rapid human uptake, reduction of Cr(VI) might not be as effective a detoxification pathway as initially thought.