Fabrication of Polyaluminium Ferric Sulfate from Bauxite Residue for Efficient Removal of Cr(VI) from Simulated Wastewater.

Bauxite residue is generated from alumina production in the alumina refining industry by the Bayer process, which requires a large amount of land resource and causes serious environmental problems. In this paper, a novel recycling strategy is proposed to rehabilitate the land and produce the polyaluminium ferric sulfate (PAFS) and siliceous gypsum byproducts from the bauxite residue. The batch experiments reveal that the maximum Cr(VI) removal efficiency of as-prepared PAFS can reach 95.80% with an initial concentration of 10.41 mg/L. In addition, the non-toxic siliceous gypsum should be an ideal raw material for cement plants. Various characterizations (e.g., SEM, FTIR, and XRD) are employed to reveal the mechanism of synthesis PAFS and their Cr(VI) removal performance. Consequently, this paper provides a deep insight into the utilization of bauxite residue as a resource and gives a new strategy for preparing PAFS and gypsum from bauxite residue.

Effects of co-contamination of heavy metals and total petroleum hydrocarbons on soil bacterial community and function network reconstitution.

Due to the accumulation of heavy metals in soil ecosystems, the response of soil microorganisms to the disturbance of heavy metals were widely studied. However, little was known about the interactions among microorganisms in heavy metals and total petroleum hydrocarbons (TPH) co-contaminated soils. In the present study, the microbiota shifts of 2 different contamination types of heavy metal-TPH polluted soils were investigated. NGS sequencing approach was adopted to illustrate the microbial community structure and to predict community function. Networks were established to reveal the interactions between microbes and environmental pollutants. Results showed that the alpha diversity and OTUs number of soil microbiota were reduced under heavy metals and TPH pollutants. TPH was the major pollutant in HT1 group, in which Proteobacteria phylum increased significantly, including Arenimonas genus, Sphingomonadaceae family and Burkholderiaceae family. Moreover, the function structures based on the KEGG database of HT1 group was enriched in the benzene matter metabolism and bacterial motoricity in microbiota. In contrast, severe Cr-Pb-TPH co-pollutants in HT2 increased the abundance of Firmicutes. In details, the relative abundance of Streptococcus genus and Bacilli class raised sharply. The DNA replication functions in microbiota were enriched under severely contaminated soil as a result of high concentrations of heavy metals and TPH pollutants' damage to bacteria. Furthermore, according to the correlation analysis between microbes and the pollutants, Streptococcus, Neisseria, Aeromonas, Porphyromonas and Acinetobacter were suggested as the bioremediation bacteria for Cr and Pb polluted soils, while Syntrophaceae spp. and Immundisolibacter were suggested as the bioremediation bacteria for TPH polluted soil. The study took a survey on the microbiota shifts of the heavy metals and TPH polluted soils, and the microbe's biomarkers provided new insights for the candidate strains of biodegradation, while further researches are required to verify the biodegradation mechanism of these biomarkers.

Evaluation of the Effects of Lime-bassanite-charcoal Amendment on the Immobilization of Cadmium in Contaminated Soil.

The effects of amendments, such as lime, bassanite, sodium phosphate, steel slag and charcoal, and their compounds on the immobilization of cadmium (Cd) are investigated. The lime-bassanite-charcoal compound shows the best remediation performance compared to other agents in conducted experiments. The optimum condition for lime-bassanite-charcoal application in contaminated soil is lime-bassanite-charcoal with a mass ratio of 1:1/3:2/3, a dose of 2% of the soil weight, and a liquid-to-solid ratio of 35%-40%; additionally, the agents should be added before water addition. The highest Cd removal rate was 58.94% (±1.19%) with a ∆pH of 0.23, which is much higher than the rates reported in previous studies. The compound amendment was used in a field experiment, demonstrating a Cd removal efficiency of 48.78% (±4.23), further confirming its effectiveness.

Coke formation and carbon atom economy of methanol-to-olefins reaction.

The methanol-to-olefins (MTO) process is becoming the most important non-petrochemical route for the production of light olefins from coal or natural gas. Maximizing the generation of the target products, ethene and propene, and minimizing the production of byproducts and coke, are major considerations in the efficient utilization of the carbon resource of methanol. In the present work, the heterogeneous catalytic conversion of methanol was evaluated by performing simultaneous measurements of the volatile products generated in the gas phase and the confined coke deposition in the catalyst phase. Real-time and complete reaction profiles were plotted to allow the comparison of carbon atom economy of methanol conversion over the catalyst SAPO-34 at varied reaction temperatures. The difference in carbon atom economy was closely related with the coke formation in the SAPO-34 catalyst. The confined coke compounds were determined. A new type of confined organics was found, and these accounted for the quick deactivation and low carbon atom economy under low-reaction-temperature conditions. Based on the carbon atom economy evaluation and coke species determination, optimized operating conditions for the MTO process are suggested; these conditions guarantee high conversion efficiency of methanol.

Generation of diamondoid hydrocarbons as confined compounds in SAPO-34 catalyst in the conversion of methanol.

Formation of adamantane hydrocarbons and their confinement in SAPO-34 caused the long induction period and the quick catalyst deactivation in methanol conversion. Via ship-in-a-bottle synthesis, adamantane and methyladamantanes could be produced from methanol conversion in the cage of 8-ring SAPO catalysts under very mild reaction conditions.