The Application of Mineral Kaolinite for Environment Decontamination: A Review

Abstract

Kaolinite clay mineral with a layered silicate structure is an abundant resource in China. Due to its advantages of excellent stability, high specific surface area and environmental friendliness, kaolinite is widely used in environment decontamination. By using kaolinite as a carrier, the photocatalytic technology in pure photocatalysts of poor activities, narrow spectral responses, and limited electron transport can be overcome, and the nano-Ag disinfectant’s limitation of the growth and aggregation of nanoparticles is released. Moreover, pure kaolinite used as an adsorbent shows poor surface hydroxyl activity and low cation exchange, leading to the poor adsorption selectivity and easy desorption of heavy metals. Current modification methods including heat treatment, acid modification, metal modification, inorganic salt modification, and organic modification are carried out to obtain better adsorption performance. This review systematically summarizes the application of kaolinite-based nanomaterials in environmental decontamination, such as photocatalytic pollutant degradation and disinfection, nano silver (Ag) disinfection, and heavy metal adsorption. In addition, applications on gas phase pollutant, such as carbon dioxide (CO2), capture and the removal of volatile organic compounds (VOCs) are also discussed. This study is the first comprehensive summary of the application of kaolinite in the environmental field. The review also illustrates the efficiency and mechanisms of coupling naturally/modified kaolinite with nanomaterials, and the limitation of the current use of kaolinite.

Synthesis Methods, Properties, and Modifications of Biochar-Based Materials for Wastewater Treatment: A Review

“…One of them is the generation of sludge containing biochar with contaminants after adsorption processes, which, sometimes, must be treated or incinerated, generating a large amount of gases that can harm the environment [2]. Likewise, the efficiency of biochar is sometimes lower than that of other types of adsorbents, like zeolites [227][228][229][230], clays [32,50,231,232], and hydrogels [233][234][235], which can be even cheaper than the carbonaceous materials.…”

Tailoring MIL-100(Fe)-derived catalyst for controlled carbon dioxide conversion and product selectivity

“…Achieving improved metal dispersion within a carbon matrix, small particle size (averaged around 3 nm), and high metal loading after the pyrolysis of MIL-100(Fe) at low temperature. 41–43 As a result, CO 2 conversion percentage was around 44.1% where paraffins were obtained with a selectivity of 99%, while the O/P ratio remained below 0.01.…”

Utilization of Waste Glass Cullet as Partial Substitutions of Coarse Aggregate to Produce Eco-Friendly Concrete: Role of Metakaolin as Cement Replacement

“…Kaolin, a raw resource in numerous industries, is transformed into metakaolin using thermal processing that chemically removes bonded water and changes the crystalline phase [45,46]. The thermal system causes moisture to leak out of the kaolin (Al 2 O 3 •2SiO 2 •2H 2 O) [47] and changes the structural parameters, leading to metakaolin, an unstructured aluminosilicate (Al 2 O 3 •2SiO 2 ) [48]. At room temperature, metakaolin combines with Ca(OH) 2 to generate the Calcium Silicate Hydrate (C-S-H) gel, which then interacts with Calcium Hydroxide (CH) to create alumina-containing stages, such as C 4 AH 13 , C 2 ASH 8 , and C 3 AH 6 [49,50].…”