Advanced treatment of wastewater with methyl orange and heavy metals on TiO2, fly ash and their mixtures

Dyes and heavy metals represent common, dangerous pollutants, resulting in large quantities in the textile finishing industry. Advanced removal of heavy metals is usually proposed via adsorption and the use of modified fly ash represents a sustainable solution. Photodegradation of dyes using anatase is largely studied and represents a process that can be up-scaled. For wastewater containing both heavy metals and dyes, an obvious treatment technology is thus the association of modified fly ash with anatase. During this process, the substrates are loaded with both pollutants and their efficiency must be quantified under these conditions. The study presents the results obtained in Cd2+ and Cu2+ removal, using fly ash (FA) with dye modified surface and its mixtures with TiO2. The FA morphology is characterised using AFM while XRD provides the crystallinity data. The adsorption parameters (contact time, wastewater volume:adsorbent mass ratio) were optimized and the adsorption mechanisms are discussed. The experimental results indicate that adsorption of cadmium and copper ions can be significantly improved by using mixtures of FA with TiO2. The best adsorption efficiency is registered on mixture with 25% of TiO2.