A comparative study for the removal of mining wastewater by kaolinite, activated carbon and beta zeolite

• The systems are cheap, efficient and fast for the removal of mining wastewater.
• Etheramine adsorption on kaolinite was strongly influenced by pH.
• Etheramine adsorption on activated carbon and H-BEA was weakly influenced by pH.
• The adsorbents may be regenerated by washing.
• Interaction adsorbate/adsorbent is more important for system etheramine/kaolinite.

The present work aimed to compare the use of kaolinite, activated carbon and beta zeolite in the removal of etheramine from water. It evaluated the influence of physical–chemical parameters on etheramine adsorption in the three adsorbent materials. The initial concentration of etheramine was 200 mg L− 1 and the water/adsorbent ratio was 1:100; the adsorption was favorable at pH 10.0. The adsorption equilibrium was reached in 30 min and the removal efficiencies of etheramine for kaolinite, activated carbon and beta zeolite were 80%, 96% and 98%, respectively. The adsorption isotherms were determined under optimized conditions and in the concentration range of 0 to 4000 mg L− 1. The etheramine adsorbed per unit mass of adsorbent was 33.5 mg g− 1, 65.5 mg g− 1 and 80.8 mg g− 1 for kaolinite, activated carbon and beta zeolite, respectively. However, comparing the amount adsorbed for monolayer formation and the available specific surface area of the adsorbent, kaolinite is the most efficient adsorbent. The etheramine adsorption isotherms are better fitted to the Langmuir model. The adsorption kinetics of etheramine on kaolinite could be explained by a pseudo second-order model, while on activated carbon and beta zeolite by a pseudo-first-order model. The results suggest that the influence of the interaction of adsorbate/adsorbent is more important for the adsorption of etheramine on kaolinite, which has a smaller specific surface area and larger pore size, than it is for the activated carbon and beta zeolite which present a larger specific surface area and smaller pore size. The adsorbents may be regenerated by washing: kaolinite showed 1.1% of loss of efficiency after the third re-use, while the activated carbon showed 1.5% after the first re-use.

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