Effect of the preparation method and metal content on the synthesis of metal modified titanium oxide used for the removal of salicylic acid under UV light

Mass-Transfer Simulation of Salicylic Acid on Weakly Polar Hyper-cross-linked Resin XDA-200 with Coadsorption of Sodium Ion

The mass-transfer process of salicylic acid on hyper-cross-linked resin XDA-200 was experimentally and theoretically studied. Undissociated salicylic acid was found to be the favorable form for salicylic acid adsorption on the resin. A pH-dependent adsorption isotherm model established in this paper could well fit the adsorption isotherm data at different pH values. Surface diffusion is the main mass-transfer mode for salicylic acid in resin particles. The salicylate anions and Na⁺ coadsorbed on the resin. The modified surface diffusion model considering the coadsorption was proposed. The model could satisfactorily fit the concentration decay curves of salicylic acid at different pH values and feed concentrations. NaOH aqueous solution at pH 12 could elute salicylic acid in the fixed bed efficiently. A pH-dependent dynamic adsorption and elution process model considering axial diffusion, external mass transfer, surface diffusion, pH-dependent adsorption equilibrium, as well as coadsorption of salicylate anions and Na⁺ was established. The model could well predict the breakthrough and elution curves at different feed concentrations. The research carried out in this paper has reference significance for optimizing the separation process of salicylic acid and its analogues.

Study on Solidification and Stabilization of Antimony-Containing Tailings with Metallurgical Slag-Based Binders

Blast furnace slag (BFS), steel slag (SS), and flue gas desulfurized gypsum (FGDG) were used to prepare metallurgical slag-based binder (MSB), which was afterwards mixed with high-antimony-containing mine tailings to form green mining fill samples (MBTs) for Sb solidification/stabilization (S/S). Results showed that all MBT samples met the requirement for mining backfills. In particular, the unconfined compressive strength of MBTs increased with the curing time, exceeding that of ordinary Portland cement (OPC). Moreover, MBTs exhibited the better antimony solidifying properties, and their immobilization efficiency could reach 99%, as compared to that of OPC. KSb(OH)₆ was used to prepare pure MSB paste for solidifying mechanism analysis. Characteristics of metallurgical slag-based binder (MSB) solidified/stabilized antimony (Sb) were investigated via X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). According to the results, the main hydration products of MSB were C-S-H gel and ettringite. Among them, C-S-H gel had an obvious adsorption and physical sealing effect on Sb, and the incorporation of Sb would reduce the degree of C-S-H gel polymerization. Besides, ettringite was found to exert little impact on the solidification and stabilization of Sb. However, due to the complex composition of MSB, it was hard to conclude whether Sb entered the ettringite lattice.

Sol-gel synthesis of carbon-doped TiO2 nanoparticles based on microcrystalline cellulose for efficient photocatalytic degradation of methylene blue under visible light

Carbon-doped titanium dioxide photocatalyst with improved performance in visible light was prepared via the typical sol-gel method. Microcrystalline cellulose (MCC) was used as carbon elements source. The prepared pure and carbon-doped TiO₂ samples were calcined at 400-650°C in air and the effect of annealing temperature on the stability of carbon ions was investigated. EDX analysis showed the presence of 5.66 wt.% carbon atoms in TiO₂ nanoparticles formed on MCC, which was attributed to the doping of carbon atoms in TiO₂ lattice. Carbon doping was also confirmed by Raman spectroscopy. According to the UV-VIS DRS analysis, the band gap of TiO₂ particles decreased from 2.96 to 2.71 eV in pure and carbon-doped TiO₂, respectively. Therefore the visible light absorbance increased to 15.05% compared to 0% absorbance in pure TiO₂. The heat treatment of carbon-doped TiO₂ nanostructures showed that carbon element could escape from the O-Ti-O lattice at temperatures higher than 600°C. According to the SEM images, synthesis of TiO₂ in presence of MCC also limited the growth of TiO₂ nanoparticles and controlled the morphology and aggregation of nanoparticles. Carbon doping improved the photocatalytic performance of TiO₂ photocatalyst compared to the pure nanoparticles in degradation of methylene blue in the aqueous phase. Carbon-doped TiO₂ attained the efficiency of 56.25%, 51.18% and 62.95% under UV, visible and solar lights, respectively, compared to 28.43%, 6.36% and 33.65% related to the pure TiO₂.