Ni doped zinc oxide nanoparticles supported bentonite clay for photocatalytic degradation of anionic and cationic synthetic dyes in water treatment

Abstract

In this study, a selective method for removal of dyes from aqueous solutions using nanocomposites of nickel doped zinc oxide nanoparticles (Ni0.02Zn0.98O) photocatalyst supported on bentonite clay was investigated. The nanocomposite was characterized with FTIR, and UV-Vis molecular spectroscopies as well as XRD, SEM and EDX analysis. Congo red (CR), methyl orange (MO) (anionic azo dyes) and crystal violet (CV) (cationic dye) were examined as target dyes. The effect of different parameters such as pH, dosage of adsorbent, contact time, and light illumination on the rate of removal of dyes were investigated and optimized. The results showed significant improvements in the removal of MO, CV, and CR by 90%, 98%, and 93%, respectively, under coupled adsorption and photocatalysis mechanisms with illumination times of 120 min for CR, and 240 min for MO and CV. The end photodegradation products were studied with GC-MS to detect the mechanism of decolorization. The kinetics of decolorization by nanocomposites are fitted well with the pseudo-first order model. Finally, the proposed method was successfully applied used to decolorize the effluent of the textile factory.