Hongjing Tian’s research while affiliated with Qingdao University of Science and Technology and other places

The catalysts were prepared by supporting cobalt ferrite (CoxFe3−xO4) on the surfaces of sphere mesoporous silica (MCM−41) nanoparticles. The electro-assisted catalytic oxidation of MgSO3 displayed an improved oxidation rate under moderate temperatures. Electric field and CoFe2O4/MCM−41 exhibited a beneficial synergistic effect because the associated MgSO3 oxidation rate is 3.38 times the oxidation rate when only the electric field was present, and 1.83 times the oxidation rate when only the catalyst was present. The cyclic voltammetry results proved that the catalysts reduced the oxidation potential of SO3²⁻ in the presence of an electric field, and increased the electron transfer rate in the oxidation. Both the X-ray photoelectron spectroscopy (XPS) characterization and free radical scavenging experiment results indicated that Co²⁺ served as the initiator in the generation of superoxide ions (O2⁻·), which was the primary active free radical responsible for the oxidation of SO3²⁻. The electron spin resonance (ESR) spectra showed that the electric field and high current density expedited the production of O2⁻·. The XPS results convincingly demonstrated that the electric field effectively alleviated the catalyst deterioration, and, as a result, significantly improved the catalyst's recyclability. Lastly, the synergistic mechanism between the electric field and the catalyst in the catalytic oxidation of MgSO3 was explored.

A novel solid bi-amine adsorbent was synthesized by simultaneously impregnating pentaethylenehexamine (PEHA) and aminoethylethanolamine (AEEA) on the surfaces of mesoporous MCM–41 nanospheres. AEEA and PEHA had a synergistic effect during the CO2 adsorption of the bi-amine adsorbent and the highest CO2 adsorption capacity was 4.03 mmol·g–1. The bi-amine adsorbent exhibited the favorable recyclability because its saturated CO2 adsorption capacity decreased by 6.20 % after the initial eight adsorption/desorption cycles while by only 2.23 % in the following seven cycles. The adsorption activation energy and the desorption activation energy were determined to be 12.53 and 16.81 kJ·mol–1, respectively. The low value of the desorption activation energy suggested an inconsiderable energy requirement in the multicycles of the adsorbent. The characterization results indicated that hydrogen bonds were formed between the hydrogen atom in hydroxyl groups of AEEA and the oxygen atom in carbonyl groups of the carbamate. The synergistic effect between AEEA and PEHA was unveiled on the CO2 adsorption of the bi-amine adsorbent. The formed hydrogen bonds facilitated the release of protons from carbamic acids, enhanced the stability of the produced carbamate anions, and thus boosted the CO2 adsorption performance.

In this work, separation and recovery of gallium from aqueous solutions was examined using acid-base bifunctional ionic liquids (Bif-ILs) in both solvent extraction and supported liquid membrane (SLM) processes. The influence of a variety of parameters, such as feed acidity, extractant concentration and metal concentration on the solvent extraction behavior were evaluated. The slope method combined with FTIR spectroscopy was utilized to determine possible extraction mechanisms. The SLM containing Bif-ILs demonstrated highly selective facilitated transport of 96.2% Ga(III) from feed to stripping solution after optimization. During the evaluation of the separation performance of SLM for the transport of Ga(III), in the presence of Al(III), Mg(II), Cu(II) and Fe(II), 88.5% Ga(III) could be transported with only 6% Fe(II) and a nil quantity of other metals co-transported. SLM exhibited excellent long-time stability in five repeated transport cycles. Highly selective transport and separation performance was achieved using the SLM containing Bif-ILs, indicating considerable potential for application in Ga(III) recovery.

A novel floating activated carbon/Cu2O/CuO(AC/Cu2O/CuO) heterojunction was synthesized by chemical method. It was used as new photocatalyst for adsorption simultaneous photocatalytic degradation of organic pollutants in water in visible light. The degradation rate of AC/Cu2O/CuO to the simulated pollutant methyl orange reaches 96.73%. And absorption wavelength of AC/Cu2O/Cu to sunlight extended from 662 nm to 765 nm. The relative molar ratio of Cu²⁺ to Cu⁺ affects its photocatalytic activity. When the relative molar ratio of Cu⁺ to Cu²⁺ is 1:1, the heterojunction impedance is reduced by 64% and gap width reduced by 0.31 eV. AC/Cu2O/CuO heterojunction improved the dissociation of photo-generated electron-hole pair. Activated carbon has PI bonds that provide fast electron and medium transfer channel. Characterization analysis show AC/Cu2O/CuO heterojunction reduced photocorrosion of Cu2O and the resistance of the carrier transportation improving visible light utilization.

Our previous work reported to simultaneously remove the alkali and alkaline earth metals, and chlorine by co-hydrothermal carbonization (co-HTC) of high-alkali coal and polyvinyl chloride (PVC) (Fuel Process Technol, 199(2020)106277). This work is to investigate on the moisture re-adsorption characteristics of those hydrochar obtained at various co-HTC operating conditions. The results show that the water re-adsorption capacity of hydrochar was decreased with the circumstance temperature rising from 20 °C to 35 °C, while it was increased with the air humidity increasing from 50% to 80%. During the co-HTC, the addition of PVC could effectively inhibit the moisture re-adsorption behavior of hydrochar resulting from the adhere of the hydrophobic PVC to the surface of hydrochar as evidenced by SEM. The circumstance temperature had a significant influence on the effective diffusivity D over the humidity. The equilibrium moisture content (EMC) and effective diffusivity (D) could be linearly correlated with surface area and most probable pore size, respectively. The EMC of hydrochar was reduced about 0.6 mg/g as the BET surface area decreased 1 m². The reduction of oxygen-containing groups could reduce the adsorption equilibrium time and adsorption heat. Besides, the higher circumstance humidity would cause hydrochar to release higher adsorption heat. As the humidity was increased from 70% to 80%, the heat released by 1 g hydrochar was increased about 13.82–19.63 kJ/mol. Due to the lower EMC and adsorption heat, 300 °C was supposed to be a suitable temperature for the co-HTC to obtain hydrophobic hydrochar.

A method was proposed for simultaneously regenerating magnesia from the Mg-based flue gas desulfurization byproducts in the power plant and generating the high concentration of sulfur dioxide. Elemental sulfur particles were evaporated to sulfur vapor and the latter one was used as the reductive agent to regenerate magnesia from the magnesium gypsum. The experiments were carried out in a successive fixed-bed system to study the concentration of sulfur dioxide in the exhaust gas and the activity of the regenerated magnesia under different reaction conditions. Sulfur vapor effectively reduced the magnesia regeneration temperature from above 950 °C to merely 650 °C. The concentration of sulfur dioxide in the exhaust gas could achieve 20% by volume when the sulfur vapor partial pressure was 1674 Pa, the regeneration temperature was 750 °C, the gas hourly space velocity was 1200 h⁻¹ and the loading of the reaction materials in the regeneration reactor was 16 g, respectively. The activity of the regenerated magnesia after the decomposition of the magnesium gypsum at 750 °C was satisfactory. Both the magnesium gypsum and the regenerated magnesia were characterized using X-ray fluorescence spectroscopy, thermogravimetric analyzer, X-ray diffraction spectroscopy, BET surface area analyzer, scanning electron microscopy, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The kinetics of the magnesia regeneration from the magnesium gypsum in the presence of the sulfur vapor was analyzed and the nucleation model was determined to be the most appropriate kinetic model. The activation energy and the pre-exponential factor were determined to be 76.51 kJ/mol and 228.66 min⁻¹, respectively. All the results demonstrate that there is considerable potential for the application of this proposed method in flue gas desulfurization process.

Plastic wastes are environmentally problematic and costly to treat, but they also represent a vast untapped resource for the renewable chemical and fuel production. Pyrolysis has received extensive attention in the treatment of plastic wastes because of its technical maturity. A sole polymer in the waste plastic is easy to recycle by any means of physical or chemical techniques. However, the majority of plastic in life are mixtures and they are hard to separate, which make pyrolysis of plastic complicated compared with pure plastic because of its difference in physical/chemical properties. This work focuses on the synergistic effect and its impact on chlorine removal from the pyrolysis of chlorinated plastic mixtures. The pyrolysis behavior of plastic mixtures was investigated in terms of thermogravimetric analysis, and the corresponding kinetics were analyzed according to the distributed activation energy model (DAEM). The results show that the synergistic effect existed in the pyrolysis of a plastic mixture of LLDPE, PP, and PVC, and the DAEM could well predict the kinetics behavior. The decomposition of LLDPE/PP mixtures occurred earlier than that of calculated ones. However, the synergistic effect weakened with the increase of LLDPE in the mixtures. As for the chlorine removal, the LLDPE and PP hindered the chlorine removal from PVC during the plastic mixture pyrolysis. A noticeable negative effect on dechlorination was observed after the introduction of LLDPE or PP. Besides, the chlorine-releasing temperature became higher during the pyrolysis of plastic mixtures ([LLDPE/PVC (1:1), PP/PVC (1:1), and LLDPE/PP/PVC (1:1:1)]. These results imply that the treatment of chlorinated plastic wastes was more difficult than that of PVC in thermal conversion. In other words, more attention should be paid to both the high-temperature chlorine corrosion and high-efficient chlorine removal in practical. These data are helpful for the treatment and thermal utilization of the yearly increased plastic wastes.

Nano-TiO2 photocatalysts doped with La–N(La–N–TiO2) were prepared by solgel method. The La–N–TiO2 was loaded on the cellulose/SiO2 composite aerogel (La–N–TiO2–CSA). La–N–TiO2–CSA had both oil absorption and oil degradation functions under the sun. The static state water contact angle is up to 148° close to superhydrophobic surface. An apparent decomposition rate of oil is 92%, which is much higher than 26% of pure TiO2. Under the visible light irradiation, the photocurrent density has increased by 50%. Characterization results show that LaONO3 was uniformly distributed in TiO2 crystal. Compared with pure TiO2, the UV–Vis DRS data showed the absorption band of La–N–TiO2 had extended to 441 nm. The La increased the valence band position and N lowered the conduction band position, which reduced the band gap of TiO2 from 3.59 to 2.81 eV. The formation of LaONO3 reduced carrier transfer resistance, and the migration rate and electron–hole separation efficiency were improved. The possible oil decomposition pathways were proposed. Graphic abstract Open image in new window