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As one of the most widely used inorganic fine powder fillers, calcium carbonate is cheap. However, considering its poor light transmittance, it is not suitable to be added to resin matrix composites that require high light transmittance. Aluminum hydroxide has good light transmission and flame retardancy, but it is more expensive than calcium carbonate. CaCO3/Al(OH)3 composites with a core-shell structure that showed a trend toward the performance of aluminum hydroxide not only improved the surface properties of CaCO3, but also increased the added value of CaCO3. In the present paper, CaCO3/Al(OH)3 composites were successfully prepared in sodium aluminate solution via heterogeneous nucleation. Four types of calcium sources, including calcite-type precipitated calcium carbonate, vaterite-type precipitated calcium carbonate, ground calcium carbonate with two different particle sizes as the precursors and supersaturated sodium aluminate solution as the substrate, have been deeply investigated in terms of their influence on the preparation of CaCO3/Al(OH)3 composites. Results showed that the calcium carbonate precursor greatly affected the formation of CaCO3/Al(OH)3 composites. Both the precipitated calcium carbonate and the small particle ground calcium carbonate are likely to undergo anti-causticization and a complexation reaction with it to generate 3CaO·Al2O3·6H2O and 3CaO·Al2O3·CaCO3·11H2O, which go against the coating of calcium carbonate with aluminum hydroxide. Within the experimental range, the use of ground calcium carbonate with a particle size of 400–500 mesh is more suitable as a precursor for the preparation of core-shell CaCO3/Al(OH)3 composites. [ABSTRACT FROM AUTHOR]

The generation of solids by aquaculture activities has led to many problems in animal welfare, environmental quality, water treatment effects and public health, such as gill and intestinal damage, water eutrophication, system components blockages and antibiotics transfers through the food chain to human; thus, effective solid wastes management is very important. The purpose of this review is to summarize the sources, characterization methods, harmfulness, removal technologies and reutilization of solids in aquaculture water, including (i) different sources of solids, such as uneaten feed, feces and debris; (ii) solids characterization based on the general parameters, particle size distribution and chemical composition; (iii) the toxicity and detriment of solids to cultured species, the environment, aquaculture system components and human health; (iv) Solids removal, effluents solids thickening and source control techniques for better solids management; and (v) various methods for the reutilization of aquacultural solid wastes for resource value‐adding. In addition to these five specific objectives, the merits and drawbacks of each method or technology and future research priorities are discussed. The present review provides an understanding of the role played by solids in aquaculture water and provides guidance for aquacultural solid wastes precision management, aquaculture practices and technological developments. Thus, solids management can be carried out based on this guidance to improve animal welfare and the stability of water treatment systems, reduce harm to the environment and public health, and enable the development of aquaculture in a sustainable way. [ABSTRACT FROM AUTHOR]

An indirect CO2 mineral sequestration involving two separated steps with acetic acid as a recycling medium provides a promising method for CO2 sequestration as well as the minimum CO2 emission for calcium carbonate production. In such an indirect route, the calcium carbonate production in the second gas-liquid reactive crystallization step has been challenged by low carbonation efficiency. This paper describes significant enhancement of the second step by coupling reactive crystallization and solvent extraction with the introduction of the organic solvent, tributyl phosphate (TBP), to the process. Based on the reaction mechanism of this enhanced carbonation process, many influencing factors including stirring speed, phase ratio, reaction time, reaction temperature, CO2 partial pressure, and the composition of the initial aqueous solution, were studied. Given the operating conditions of 60 min reaction time, 500 rpm stirring speed, organic-to-aqueous phase volume ratio of 1, 80 °C reaction temperature, 4.0 MPa CO2 partial pressure, and initial pH of 7, the obtained crystallization conversion in the second step was found to increase from 20% to above 50%, with the incorporation of TBP and the addition of magnesium acetate. [ABSTRACT FROM AUTHOR]

The typical features for an integrated iron & steelmaking industry are high energy consumption and CO2 emission. The traditional BF-BOF process in an integrated Iron and steelmaking enterprise produces a large amount of residual heat and energy, which has great potential for recovery and abatement potential of CO2 emissions. In this paper, for an integrated Iron & steelmaking enterprise of 10 million tons per year in capacity, the residual heat and energy recovery analysis was conducted. It is indicateded that the residual heat and energy can be recovered as electric power by using present advanced process technology. By means of the distributed power generation, the residual heat and energy can be recovered, with a power generation capacity of 419.5 kWh per ton steel product. Accordingly, the abatement potential of CO2 emissions for an integrated iron & steel-making enterprise was also evaluated, which indicated that about 398.5 kg CO2 could be reduced per ton steel product. [ABSTRACT FROM AUTHOR]

Large amounts of selective catalytic reduction (SCR) denitrification catalysts with poor mechanical property are disposed and difficult to be regenerated, resulting in environmental pollution. For spent SCR denitrification catalyst, the ratio of V 4+ /V 5+ decreased by about 45% and Fe impurity increased >10 times, which influenced the recycling of the supporter. Selective leaching of V and Fe by oxalic acid and its reaction mechanism were investigated. Under the optimized leaching condition: oxalic acid concentration of 1.0 mol/L, reaction temperature of 90 °C, liquid-to-solid ratio of 20 mL/g, <75 μm particle size and leaching time of 180 min, the leaching efficiencies of V and Fe reached over 84% and 96%, respectively. The reaction mechanism for the selective leaching of these metals was determined through UV-VIS spectrophotometry and CO 2 emission analyses. After dissolution and complexation, VO 2 + and Fe 3+ were reduced to water-soluble cations VO 2+ and Fe 2+ . When V and Fe was in the specific forms of VOC 2 O 4 and Fe(C 2 O 4 ) 2 2− at 0.33 pH, high leaching efficiency was obtained. It indicated that redox reactions led to the broken of dissolution and complexation equilibriums for VO 2 + , VO + and Fe 3+ . For W and Ti, only dissolution and complexation reactions occurred and the leaching efficiency was limited by the solubility. The leaching residue with anatase TiO 2 was recovered as carrier and used for synthesis of a new SCR catalyst. [ABSTRACT FROM AUTHOR]

Alumina was leached from high-alumina coal fly ash with a NH 4 HSO 4 + H 2 SO 4 mixed solution. The leaching behavior was systematically investigated, as were factors such as mixed solution composition and concentration, reaction time and temperature, and liquid-to-solid ratio. In optimal conditions, the alumina extraction ratios can reach 87.8%, 91.1%, and 87.5% for the three different sources of coal fly ash, respectively. The phases and morphology of the raw materials and residues were also analyzed through X-ray diffraction and scanning electron microscopy–energy dispersive spectroscopy. Results showed that mullite, which is the main form taken by alumina in high-alumina coal fly ash, can be effectively decomposed to release the alumina and induce a new amorphous silica phase in mixed solution. [ABSTRACT FROM AUTHOR]