Ni(II) removal from wastewater by solar energy-degreased spent coffee grounds

Abstract

Coffee is one of the most favorite drinks, and its consumption results in an enormous amount of spent coffee waste in Taiwan. In this study, the feasibility of Ni(II) removal by solar energy-degreased spent coffee grounds (SCG) was evaluated. The Taguchi experimental design was applied to determine the optimum adsorption condition. The controllable factors including the treatment procedure of SCG, initial concentration of Ni(II), SCG dose, contact time, and temperature were optimized. The results showed that the order of importance of the controllable factors was the concentration of Ni(II) > SCG dose > SCG treatment procedure. For the influence of the treatment procedure of SCG, the removal efficiency of Ni(II) in descending order was SCG degreased by solar energy > washing by boiling DI water > washing by cold DI water. Moreover, both results of Langmuir and Freundlich adsorption isotherms also showed that solar energy-degreased SCG was the most effective adsorbent for Ni(II) removal in wastewater. The maximum adsorption capacity q m of Ni(II) by solar energy-degreased SCG was 4.29 mg/g, about twice of that by non-degreased SCG. Hence, Ni(II) could be effectively removed from wastewater by utilizing solar energy and SCG, a great reduction in energy expenditure and coffee waste.