Evaluation of leaching characteristic and kinetic study of lithium from lithium aluminum silicate glass-ceramics by NaOH

The behavior and mechanism of Li leaching from lithium aluminum silicate glass-ceramics which can be used as a secondary source of Li using aqueous NaOH solution was investigated. The Li leaching efficiency is increased with increasing concentration of NaOH, specific surface area, and reaction temperature. When leached under optimum conditions, 2 mol/L NaOH, 53 μm particle undersize, 1:10 solid/liquid ratio, 250 r/min stirring speed, 100°C reaction temperature, 12 hr, the Li leaching efficiency was approximately 70%. However, when the leaching experiment was performed for 48 hr, the concentration of Li⁺ ions contained in the leach liquor decreased from 1160 to 236 mg/L. To investigate the origin of this phenomenon, the obtained leach residue was analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. These analyses show that zeolite was formed around the lithium aluminum silicate glass-ceramics, which affected the leaching of by adsorbing Li⁺ ions. In addition, using the shrinking-core model and the Arrhenius equation, the leaching reaction with NaOH was found to depends on the chemical reaction of the two reactants, with a higher than 41.84 kJ/mol of the activation energy.     

Profiles and removal efficiency of polycyclic aromatic hydrocarbons by two different types of sewage treatment plants in Hong Kong

Sewage discharge could be a major source of polycyclic aromatic hydrocarbons(PAHs) in the coastal waters. Stonecutters Island and Shatin Sewage Treatment Works(SCISTW and STSTW)in Hong Kong, adopted chemically enhanced primary treatment and biological treatment,respectively. This study aimed at(1) determining the removal efficiencies of PAHs,(2) comparing the capabilities in removing PAHs, and(3) characterizing the profile of each individual PAHs, in the two sewage treatment plants(STPs). Quantification of 16 PAHs was conducted by a Gas Chromatography. The concentrations of total PAHs decreased gradually along the treatment processes(from 301 ± 255 and 307 ± 217 ng/L to 14.9 ± 12.1 and 63.3 ± 54.1 ng/L in STSTW and SCISTW, respectively). It was noted that STSTW was more capable in removing total PAHs than SCISTW with average total removal efficiency 94.4% ± 4.12% vs. 79.2% ± 7.48%(p 0.05). The removal of PAHs was probably due to sorption in particular matter, confirmed by the higher distribution coefficient of individual and total PAHs in solid samples(dewatered sludge contained92.5% and 74.7% of total PAHs in SCISTW and STSTW, respectively) than liquid samples(final effluent-total contained 7.53% and 25.3% of total PAHs in STSTW and SCISTW, respectively).Despite the impressive capability of STSTW and SCISTW in removing PAHs, there was still a considerable amount of total PAHs(1.85 and 39.3 kg/year, respectively for the two STPs) being discharged into Hong Kong coastal waters, which would be an environmental concern.     

Exposure to PCBs, through inhalation, dermal contact and dust ingestion at Taizhou, China--a major site for recycling transformers

Air samples containing gaseous and particulate phases were collected from e-waste workplaces and residential areas of an intensive e-waste recycling area and compared with a reference site. The highest total concentration of PCBs was detected at transformer recycling workshops (17.6 ng m(-3)), followed by the residential area (3.37 ng m(-3)) at Taizhou, and the lowest was obtained at the residential area of the reference site, Lin'an (0.46 ng m(-3)). The same trend was also observed with regards to PCB levels in dust samples. The highest average PCBs level of 2824 ng g(-1) (dry wt) was found in the transformer recycling workshops, and was significantly higher than that of residential areas of Taizhou (572 ng g(-1) dry wt) and Lin'an (42.4 ng g(-1) dry wt). WHO-PCB-TEQ level in the workshops of Taizhou was 2216 pg TEQ(1998)g(-1) dry wt or 2159 pg TEQ(2005)g(-1) dry wt, due to the high abundance of PCB 126 (21.5 ng g(-1) dry wt), which contributed 97% or 99% of WHO-PCB-TEQs. The estimated intake of PCBs via dust ingestion and dermal absorption by transformer recycling workers were 77.5×10(-5) and 36.0×10(-5) pg WHO-PCB-TEQ(1998)kg(-1)d(-1), and 67.3×10(-5) and 31.3×10(-5) pg WHO-PCB-TEQ(2005)kg(-1)d(-1), respectively.     

The outbreak of COVID-19 in Taiwan in late spring 2021: combinations of specific weather conditions and related factors

Environmental Science and Pollution Research - This study aimed to investigate the impact of weather conditions on the daily incidence of the COVID-19 pandemic in late spring 2021 in Taiwan, which...     

Remediation of pharmaceuticals from contaminated water by molecularly imprinted polymers: a review

Environmental Chemistry Letters - The release of pharmaceuticals into the environment induces adverse effects on the metabolism of humans and other living species, calling for advanced remediation...     

Quantile relationship between globalization,financial development,economic growth,and carbon emissions: evidence from Vietnam

Environmental Science and Pollution Research - Environmental quality and economic activity have a strong relationship. Carbon emissions remain one of the world’s most dangerous environmental...     

Characterization of Cu2+ adsorption for eco-hydroxyapatite derived from limestone sludge via hydrothermal synthesis

Journal of Material Cycles and Waste Management - This study developed a novel approach to the hydrothermal synthesis of eco-hydroxyapatite (eco-HPA) from recycled limestone sludge for the removal...     

Sustainable ternary cement blends with high-volume ground granulated blast furnace slag–fly ash

Environment, Development and Sustainability - Coal fly ash and granulated ground blast furnace slag (GGBS) are more widely used as supplementary cementitious materials in cement production. This...     

Optimized thermochemical detoxification of asbestos-containing waste using chemical additives and microwave heat treatment

Journal of Material Cycles and Waste Management - Owing to the increasing ACW generation, asbestos detoxification and recycling technologies are required for environmental and economic reasons....