Removal of tungsten from electroplating wastewater by acid- and heat-treated sepiolite.

In this study, the removal of tungsten from electroplating wastewater by adsorption on sepiolite has been investigated. To improve its performance, the natural sepiolite, was treated using H2SO4, followed by a heat treatment. The results obtained from the adsorption experiments showed that the acid- and heat-treated sepiolite had much higher adsorption for tungsten compared to the untreated (natural) sepiolite. The pH and temperature were important parameters in the adsorption process: the tungsten adsorption onto the acid- and heat-treated sepiolite increased at a lower pH and higher temperature, and the maximum adsorption capacity of 48.3 mg/g was obtained at pH 4.0, 55°C, initial concentration of tungsten of 300 mg/L, and the sepiolite to liquid ratio of 0.5 g/100 mL. The acid- and heat-treated sepiolite was applied to electroplating industrial wastewater containing 265 mg/L tungsten, under the conditions of pH ≤ 6, 25–55°C, more than 98% of tungsten was removed. It was concluded that the acid- and heat-treated sepiolite is a potential adsorbent that can be commercially used to remove the residual tungsten in industrial wastewater. [ABSTRACT FROM PUBLISHER]