Mechanism investigation on selective adsorption of fabric loaded with calcium silicate for organic dyes

Selective adsorption plays an important role in the resource utilization of dye wastewater. Hydrated calcium silicate (CSH), as an ideal adsorption material, is successfully compounded on the surface of polypropylene (PP) fibric by quasi-solid-phase method, and porous calcium silicate film is formed on the surface of PP fabric. The contact angle of the surface of PP fibers is changed from 130.7° to 62.4° due to the hydrophilic characteristics of CSH and polyvinyl alcohol. The adsorption for dyes shows obvious selectivity, and the removal ratio for methylene blue can reach more than 90%, while there is almost no adsorption for methyl orange. The obvious selectivity can be attributed to the electrostatic interaction between CSH and dyes. CSH contains silicate anion chains, resulting in a large number of negatively charged sites distributed on the surface, which may be the main reason for the adsorption for cationic dyes through electrostatic interactions. The investigation of adsorption kinetics shows that the formation of coordination bonds between calcium silicate and methylene blue will also lead to further enhancement of adsorption capacity.