One-step hydrothermal synthesis of TiO2-supported clinoptilolite: An integrated photocatalytic adsorbent for removal of crystal violet dye from aqueous media

Abstract

The TiO2-supported clinoptilolite (TiO2/CP) was synthesized via in-situ hydrothermal crystallization of CP in TiO2 dispersion medium to prepare an integrated photocatalytic adsorbent (IPCA). The micro-structural features and textural parameters of obtained TiO2/CP were characterized via X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope, Fourier transform infrared spectroscopy, inductively coupled plasma-optical emission spectrometry, BET-isotherm, UV–vis spectrophotometer and Malvern zetasizer. The results showed a well dispersion and immobilization of anatase TiO2 particles on the surface of leaf-like CP, and low pH value of point of zero charge (pHpzc) i.e. 2.20 (SCA3) revealed a highly negatively charged surface. The synthesized TiO2/CP were used as IPCAs for removal of crystal violet (CV) dye, showing a higher rate of adsorption (46 % removal in 10 min) followed by a relatively low rate of photocatalytic degradation (49 % degradation in 120 min). TiO2/CP (SCA3) significantly improved the removal efficiency: 95 % of CV dye was removed within 150 min during both adsorption and degradation using 0.2 g/L dose at pH 6, whereas only 59 and 31 % of the dye was removed by CP and TiO2 alone respectively. Adsorption and degradation kinetics of CV dye were found to follow pseudo second and pseudo first order models, respectively, and the equilibrium adsorption results fitted Dubinin-Radushkevich model. The thermodynamic parameters (ΔGads, ΔHads, and ΔSads) of adsorption process exhibited that adsorption is physical, spontaneous, exothermic and leads to higher entropy.