Environmentally Friendly Treatment of Coal‐Bearing Kaolin by Polyhydroxy‐Iron for Anionic Dye Removal

Abstract

Clay material such as kaolin is considered great candidate in industrial water treatment due to its structural properties and abundancy. However, material treatment procedures aimed for adsorption efficiency improvement are generally energy consuming and causes secondary environment contaminations. In the present study, a cost‐effective kaolin modification technique based on polyhydroxy‐iron (PHFe(III)) treatment is applied to coal‐bearing kaolin clay (KC). The modified adsorbent (PHFe(III)/KC) shows a two fold increase in specific surface area and renders a 75 mg/g Congo Red (CR) dye uptake amount which significantly outperforms that of the raw KC (∼12 mg/g). Importantly, the modification process involves mild heating and gentle chemical reaction which is environmental benign, especially under large scale adsorbent treatment. The effect of the PHFe(III)/KC preparation conditions, adsorption time, the initial solution pH and the initial concentration of CR on the adsorption capacity of the adsorbents was investigated. Adsorbent characterization shows successful grafting of PHFe(III) which likely changes the surface property and increases the affinity between the adsorbent and organic dyes. The comparatively high dye adsorption capability and good regeneration shows promising application of PHFe(III)/KC in industrial waste water treatment.

Adsorption Behavior of Polyhydroxy‐Iron‐Modified Coal‐Bearing Kaolin for Fluoride Removal

“…The Langmuir isotherm model was employed for monolayer-based adsorption, where adsorption occurs at identical homogeneous sites within the adsorbent, and the Freundlich model was used to describe multilayer adsorption onto a heterogeneous surface. [17] The fitting parameter values are shown in Table 3. Comparing the R 2 values of the two model fitting equations, it is found that the R 2 of the Freundlich equation is approximately 0.97, which is obviously better than the Langmuir equation fitting results.…”

“…The results showed that polyhydroxy-iron-modified kaolin has an excellent adsorption efficiency of 75 mg g À 1 , which is significantly higher than that of raw kaolin (12 mg g À 1 ). [17] Fluorine is the most active halogen element located in group VIIA in the second-to-last column of the periodic chart. Fluorine has a high electronegativity and can react with almost all other elements; fluorine is mostly present as an inorganic compound.…”

FeNP-loaded coal-bearing kaolin catalysts for the direct esterification of benzoic acid with cyclic ether via C(sp3)-H bond activation

“…Herein, our research group successfully prepared palladium nanoparticle-loaded kaolin and found that it has excellent catalytic activity for the directed C-H functionalization of arylpyrazoles (25). Additionally, in previous work, we successfully prepared polyhydroxy-ironmodified coal-bearing kaolin via an environmentally friendly method for the adsorption removal of anionic dyes from water (26). In this work, we synthesized a series of iron nanoparticle-loaded coal-bearing kaolins and researched the heterogeneous catalytic activity for direct esterification to form C-O bonds via activation of inactive C(sp 3 )-H bonds of cyclic ether by CDC with aryl carboxylic acid.…”