In this study, the adsorption of neutral red (NR) on the spent ground coffee (SGC) was examined. The effect of various parameters such as pH and adsorbent dose on the removal of NR was investigated. The removal ratios of NR (25 and 40 mg/L) on SGC after 2 h were 95.6 and 90.2%, respectively. The removal ratio of NR is increased by increasing the pH value. Equilibrium data fitted very well in a Langmuir isotherm equation, the adsorption capacity of NR was 136.98 mg/g for SGC. The adsorption mechanisms can be contributed by hydrophobicity interaction at the interface occurs between NR and SGC. The present study shows that the SGC is an inexpensive and easily used NR adsorbent.

Yingjie Dai, Kexin Zhang, Danfeng Zhang and Yanjun Chen