Jia (2021) FeNP-loaded coal-bearing kaolin catalysts for the direct esterification of benzoic acid with cyclic ether via C(sp 3

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.