Ash produced by biomass power plants has great potential for the removal of heavy metal ions from aqueous solution. The pollution of toxic heavy metals to water is a worldwide environmental problem. Discharges containing copper, in particular, are strictly controlled because the excessive copper can cause serious harm to the environment and human health. This work aims to investigate the adsorption characteristics of copper ions in aqueous solution by biomass ash and the modified products, and to evaluate their potential application in water pollution control. The biomass ash was modified with a mesoporous siliceous material and functionalized with 3-aminopropyltriethoxysilane. The surface properties of the biomass ash and the new matrix were studied to evaluate their adsorption property for Cu ions at different pHs, initial metal concentrations and the thermodynamic and kinetic were studied. The chemical and morphological properties of this modified material are analyzed; the specific surface area of the modified biomass ash was nine times that of the initial ash. Both of the two materials showed a strong affinity for Cu, and the Langmuir model could best represent the adsorption characteristics of Cu on the two kinds of materials. The adsorption capacity of copper on the material increased with the increase of pH and pH 6 was the optimum pH. Thermodynamic analysis results showed that the adsorption of Cu was spontaneous and endothermic in nature. The adsorptions of Cu onto the modified biomass ash followed pseudo-second-order kinetics.
Phytoremediation is a potential cost-effective technology for remediating heavy metal-contaminated soils.
Smelter-impacted soils often result in soil degradation and the destruction of the soil structure. Although soil aggregate typically plays a crucial role in soil structure, the influence of phytoremediation on soil aggregate structure stability and stoichiometric characteristics remains unclear. To study the influence of phytoremediation on soil aggregate structure, stability and stoichiometric characteristics, a 3-year in situ experiment was conducted. After hydroxyapatite was applied, Elsholtzia splendens, Sedum plumbizincicola, and Pennisetum sp. were planted in a smelter-impacted soil. After 3 years, the soil aggregate structure, stability, and stoichiometric of chemical elements were analyzed. The results showed that the three phytoremediation treatments increased the content of >0.25 mm mechanically-stable (DR0.25) and water-stable (WR0.25) aggregates by 6.6%–10.4% and 13.3%–17.5%, respectively. Aggregate mean weight diameter (MWD), geometric mean diameter, and aggregate stability rate (AR, %) were significantly increased, and the soil mechanically stable aggregate fractal dimension (D) was significantly reduced after the 3-year remediation. Soil total nitrogen and phosphorus in aggregates with different particle sizes were significantly increased by 11.4%–46.4% and 107%–236% after different plant treatments. For the stoichiometric characteristics of the aggregates, the combined remediation only significantly reduced the value of N:P and C:P in different particle size aggregates and had no significant effect on the C:N in all particle size aggregates. Meanwhile, the combined remediation of hydroxyapatite and Elsholtzia splendens, Sedum plumbizincicola, and Pennisetum sp. in heavy metal heavily contaminated soil could reduce the availability of Cu and Cd by 54.1%–72.3% and 20.3%–47.2% during the 3 years, respectively. In summary, this combined remediation method can be used for the remediation of farmland that is contaminated by heavy metals.
The COVID-19 pandemic has caused a global public health crisis. There is a pressing need for evidence-based interventions to address the devastating clinical and public health effects of the COVID-19 pandemic. The Chinese scientists supported by private and government resources have adopted extensive efforts to identify effective drugs against the virus. To date, a large number of clinical trials addressing various aspects of COVID19 have been registered in the Chinese Clinical Trial Registry (ChiCTR), including more than 200 interventional studies. Under such an urgent circumstance, the scope and quality of these clinical studies vary significantly. Hence, this review aims to make a comprehensive analysis on the profiles of COVID-19 clinical trials registered in the ChiCTR, including a wide range of characteristics. Our findings will provide a useful summary on these clinical studies since most of these studies will encounter major challenges from the design to completion. It will be a long road for the outcomes of these studies to be published and international collaboration will help the ultimate goals of developing new vaccines and anti-viral drugs.
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