Removal of Cadmium from Aqueous Solution by Nano Composites of Bentonite /TiO 2 and Bentonite/ZnO Using Photocatalysis A
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ORIGINAL PAPER
Removal of Cadmium from Aqueous Solution by Nano Composites of Bentonite /TiO2 and Bentonite/ZnO Using Photocatalysis Adsorption Process Hossein Abbasi 1 & Farhad Salimi 1 & Farhad Golmohammadi 2 Received: 31 August 2019 / Accepted: 25 December 2019 # Springer Nature B.V. 2019
Abstract In this study, bentonite/TiO2 and bentonite/ZnO nanoparticles were used for studying the cadmium removal from the aqueous solution. The experiments were done in a batch condition under solar light. The nanoparticles characteristics were determined using analytical devices such as scanning electronic microscopy (SEM), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and the N2 absorption. The optimum condition of the adsorption process was obtained at an initial concentration of 6 ppm, time of 6 h, 45 °C temperature, 4 g/L bentonite/ZnO (pH = 5) and 2 g/L for bentonite/TiO2 (pH = 7). Also, the cadmium removal increased for bentonite/TiO2 adsorbent with increasing the light intensity but it had no effect on the bentonite/ZnO adsorbent. In this work, the adsorption isotherm and kinetics were investigated and results showed that the adsorption process followed better by Temkin isotherm and the adsorption kinetics better described by the pseudo-second-order model. Keywords Adsorption . Bentonite . Cadmium . Bentonite/ZnO . Bentonite/TiO2 . Adsorption isotherm and kinetics
1 Introduction Water pollution is a major environmental challenge that has attracted the attention of many researchers [1]. Today, one of the worrying matters is discharge of the heavy metals into aquatic systems. Metals of Pb, Hg, Cr, Ur, Se, As, Zn, Cd, Co and Ni are known as toxic compounds and released into the environment in small quantities can pose serious risks to human health [1–3]. Metals accumulate in different tissues of living organisms and cause various disabilities and diseases [4]. A major cause of heavy metal release into the environment in recent years has been rapid industrialization [5]. The existence of cadmium in aquifers is a risk to human health and the aquatic ecosystem. The nervous system, kidneys, and re-
* Farhad Salimi [email protected] 1
Department of Chemical Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
2
Department of Chemistry, Basic Science, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
productive system can be damaged by cadmium [6]. According to global standards, the maximum limit for cadmium in drinking water is 0.005 mg/L [7]. Various effective technologies have been employed for the removal of heavy metals [8–13] and hazardous azo dye [14–24] from wastewater, including ion exchange, filtration, chemical precipitation, solvent extraction, and sorption. However, these techniques have many limitations include sludge production and high disposal cost, low efficiency, sensitive operating conditions [25]. Although various methods have been developed for the removal of toxic metal ions, adsorption is conside
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