Pollution of heavy metals has become a serious environmental problem and it needs to be solved as soon as possible. Diatomite is a kind of biogenic rock and it is siliceous and sedimentary. There is abundant diatomite resource in China. Diatomite has distinctive structure of diatom monoblock. It has strong adsorbability, its specific area is large and it has high porosity. Its surface adheres a lot of active groups and negative charge. Diatomite with proper modification would show outstanding absorption effect of heavy metal ions. This paper reviewed the absorption efficiency of heavy metal ions on diatomite modified by metallic oxide, acids and bases, acticarbon, calcium carbonate and organics, the results would offer references for related researches. At last, this paper takes the outlook for the modified methods and application prospects of diatomite in wastewater treatment of heavy metals.
Talc was modified by aluminate coupling agent (ACA) before filling it into high density polypropylene (HDPP) to prepare talc/HDPP composites. Scanning electron microscopy (SEM), wear testing machine, electronic universal testing machine, and impact testing machine were used to analyze the surface modification and the effects of modified talc on friction and mechanical properties of modified talc/HDPP composites. The results indicate that after modified the lamellar structure of talc particles are open and the dispersion of particles are improved, and the edges and corners of surface become softer. Friction properties indicate that when the talc content is 8 wt%, both µ and K are at a lower value, which show that have better wear resistance. The frictional surface is relatively smooth and no furrow trace has found. Mechanical properties show that with talc content increasing, tensile strength and flexural strength of composites increase.
Cerebral contusions were the primary risk factor for MEMR complaints in chronic complicated mTBI. Early preventive psychological intervention might be necessary for patients with complicated mTBI and cerebral contusions.
In this study, calcium carbonate was used to coat and link the surface of diatomite for the formation of a novel modified adsorbent (referred to as Ca–diatomite). Various analytical techniques were used to characterize structure and mechanisms of modification and adsorption process, like Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). Results showed that that Calcium carbonate had been successful grafted onto the surface of diatomite after modification, and Calcium carbonate modification improved the adsorption performance of diatomite for the removal of lead (II) ions from aqueous solution. Ca–diatomite adsorption isotherms and adsorption kinetics were also been studied. The adsorption isotherms and the kinetic data were best fitted with the Langmuir model and pseudo-second-order kinetics, respectively.
Owing to the efficient predetermination, specific recognition and wide applicability, metal ion imprinting technology, apply to the wastewater treatment. The principles, synthesis strategies of ion imprinting and typical heavy metal ion imprinted polymers (IIPs) are introduced in the review. Finally, it is pointed out that the futures research problems to be solved and the development direction of metal ion imprinting technology.
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