Preliminary investigation of mixed adsorbents for the removal of copper and methylene blue from aqueous solutions

• Multi-adsorbent systems containing tea waste and dolomite have been tested.
• The effects of contact time, solution pH and adsorption isotherms were investigated.
• The adsorption processes of Cu ad MB were favourable at the investigated conditions.
• Adsorption capacities of DO and TW:DO for Cu and MB were 237.7 and 150.4 g g–1.
• The chemical adsorption was the main control process for the TW and DO materials.

With most recent studies being focused on the development of advanced chemical adsorbents, this paper investigates the possibility of using two natural low-cost materials for selective adsorption. Multi-adsorbent systems containing tea waste (TW) and dolomite (DO) have been tested for their effectiveness in the removal of copper and methylene blue from aqueous solutions. The effects of contact time, solution pH and adsorption isotherms on the sorption behaviour were investigated. The Langmuir and Freundlich isotherms adequately described the adsorption of copper ions and methylene blue by both materials in different systems. The highest adsorption capacities for Cu and MB were calculated as 237.7 mg/g at pH 4.5 and 150.4 mg/g at pH 7 for DO and TW:DO respectively. Tea waste and dolomite were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy and Energy dispersive X-ray analysis. The removal of Cu and MB by dolomite was mainly via surface complexation while physisorption was responsible for most of the Cu and MB adsorption onto tea waste. Identifying the fundamental mechanisms and behaviour is a key to the development of practical multi-adsorbent packed columns.