Surface modification of spent coffee ground using phosphoric acid for enhancement of methylene blue adsorption from aqueous solution

In this study, the surface of spent coffee ground (SCG) was activated using phosphoric acid to increase the removal efficiency of methylene blue (MB) in aqueous solution, which is one of the harmful substances emitted in the industrial process. According to FT-IR analysis, after phosphorylation of SCG (PSCG), P = O group, P-O-C (aromatic) bond, P = OOH and P-O-P were newly introduced on the surface of the adsorbent, and the peaks of carboxyl groups and OH-group were large and broad. In addition, the surface area and mesopore range of the PSCG adsorbent were increased, and the structure changed, which enabled easy adsorption of MB. The process of adsorbing MB from aqueous solution using PSCG was more suitable for the PSO and Langmuir models, and the adsorption process was closer to chemisorption than physical adsorption. The maximum adsorption capacity of PSCG was 188.68 mg/g. As a result of the reuse test, PSCG showed excellent performance with a high removal efficiency of 90% up to 4 consecutive uses. PSCG modified with phosphoric acid, an abundant lignocellulose-based biosorbent that is readily available everywhere, is a promising adsorbent capable of adsorbing MB in aqueous solution.

Automated summary

In this study, activated spent coffee ground (SCG) was used as an adsorbent to enhance the removal efficiency of methylene blue (MB) in aqueous solution. The activated SCG exhibited new functional groups on its surface, increased surface area and mesopore range, and changed structure, which facilitated the adsorption of MB. The adsorption process followed chemisorption and fitted well with PSO and Langmuir models. The maximum adsorption capacity of the activated SCG was 188.68 mg/g. Furthermore, the activated SCG showed excellent performance and high reusability in consecutive uses.