Construction of hydroxyethyl cellulose/silica/graphitic carbon nitride solid foam for adsorption and photocatalytic degradation of dyes

In the present study, novel hydroxyethyl cellulose/silica/graphitic carbon nitride (HEC/SiO2/C3N4) solid foams with hierarchical porous structure have been successfully fabricated with gas bubbles template combination with freeze-drying method. Compared with HEC/SiO2/C3N4-50 without gas foaming, the HEC/SiO2/C3N4-80 with air bubbles template had larger pore volume and higher porosity and specific surface area, which not only exhibited faster adsorption rate, but also presented higher saturated adsorption capacity towards methylene blue (MB) and methyl violet (MV). From the experimental results, it was found that HEC/SiO2/C3N4-80 had high adsorption capacities of 132.45 mg/g and 206.62 mg/g for MB and MV, respectively, and the adsorption process fitted the Langmuir adsorption isotherm and pseudo-second-order rate equation. Additionally, benefiting from its higher adsorption capacity and light-harvesting capability, HEC/SiO2/C3N4-80 exhibited relatively higher photocatalytic degradation efficiencies against MB and MV under visible light irradiation than HEC/SiO2/C3N4-50. More importantly, compared with the bare g-C3N4 powder, the HEC/SiO2/C3N4 solid foams could be more easily separated from the treated water, which facilitated their recycle and reuse. Therefore, the good adsorption capacity, high photocatalytic degradation activity and recyclability of the HEC/SiO2/C3N4 solid foam made it a promising candidate for the removal of organic dyes from wastewater.