Coffee residue-based activated carbons for phenol removal

Abstract

This work was aimed to evaluate the adsorptive properties of activated carbons from coffee residue for phenol removal. The coffee residue was activated using H3PO4 and KOH, and the resultant activated carbons were characterized for surface area and functional groups. The values of surface area were recorded as 1,030 m2/g and 399 m2/g for H3PO4- and KOH-activated carbons, respectively. The maximum capacity for phenol removal is comparable for both activated carbons at 43 mg/g. The pores might be inaccessible due to electrostatic repulsion by surface functional groups and hydroxyl anions. The second stage in a two-stage adsorber design is necessary to accomplish the process with high performance and minimum dosage of activated carbon. Coffee residue is a promising activated carbon precursor for phenol removal.

Malachite green adsorption by calcium-rich crab shell char via two-stage adsorber design

“…Similarly, C1 is smaller at targeted C2 = 50 mg/L, and the magnitude surges with increasing C2. A small C1 implies a more adsorbent mass to be consumed in stage-1 to bring the removal of dye in stage-2 at low equilibrium concentration [13,15]. It highlights the effectiveness of two-stage batch adsorber design at industrial scale to meet the desired performance of highly concentrated dye effluent using crab shell char [14,17,18].…”

“…To treat 250 mL effluent, stage-1 adsorber requires 0.205 g biochar to decrease the concentration from 6584 mg/L to 1484 mg/L, while stage-2 needs 0.047 g biochar to accomplish the equilibrium at concentration of 350 mg/L. Thus, the total adsorbent mass required for twostage adsorber is 0.252 g, that is lower than that of onestage adsorber which consumes 0.257 g. At any volumes, the adsorbent mass is always bigger at stage-1 because the high concentration gradient is necessary to reduce the burden in stage-2 in attaining the equilibrium [15]. Figure 3 explains the relationships between the intermediate concentration, C1 and the initial concentration, Co at different performances and stage-2 concentrations, C2.…”

“…It exhibits a 79 % reduction in adsorption process as compared to one-stage adsorber. The feasibility of a two-stage adsorber in minimizing the total contact time is significant because an additional unit of adsorber minimizes not only the total adsorbent mass but also improves the economics and efficiency of dye removal for industrial wastewater treatment [15,16]. Figure 7 shows the parametric effects by RSM.…”

“…In a two-stage adsorption, two consecutive batches are employed to attain the same equilibrium concentration or removal of the same effluent volume, wherein the dosage varies depending on the intermediate concentration leaving the stage-1 upon entering the stage-2. However, only limited application of such data has been directed towards the design of adsorption treatment system [11][12][13][14][15][16]. Furthermore, the two-stage adsorber design for highperformance adsorbents is not widely documented in literature, so restricting their potential to be exploited for the wastewater treatment applications.…”