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

Abstract

In this study, the surface of the spent coffee grounds (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 industrial processes. According to Fourier transform infra-red analysis, after phosphorylation of the 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 pseudo-second order 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 four 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.

Eliminating waste with waste: transforming spent coffee grounds into microrobots for water treatment

“…The uncoated SCGs have a rough, highly textured surface with heterogeneous porosity and flaky protrusions, resulting in a large specific surface area. 46,48,50,52 This feature makes them highly effective for water purification, as it enhances contact between the SCGs and the contaminants, resulting in a more efficient purification process. The Fig.…”

“…The uncoated SCGs have a rough, highly textured surface with heterogeneous porosity and flaky protrusions, resulting in a large specific surface area. 46,48,50,52 This feature makes them highly effective for water purification, as it enhances contact between the SCGs and the contaminants, resulting in Scheme 1 (A) The SCGs were collected after brewing and desiccated in an oven. The dehydrated SCGs were immersed in an alcoholic mixture of iron oxide nanoparticles (IONPs) for 2 h. The IONPs bind to SCG surfaces as a result of hydrogen bonding between the oxygen elements in IONPs and hydroxyl (-OH) functional groups found on the surface of SCG.…”

“…46,47 Since they are widely available, SCG bio-wastes are a convenient and cost-effective starting material for making CoffeeBots. In previous research, coffee grounds subjected to carbonization at high temperature 48–51 or chemical modifications 52–56 showed potential for eliminating oil spills, 48,49,54 organic dyes, 50,52,55 endocrine disruptors, 57 antibiotics, 57,58 heavy metals 51,53,56 and MPs. 59 However, there remains an unmet need for a cost-effective manner to render SCGs amenable to magnetic manipulation and steering, which will enhance their degradation performance and enable magnetic recollection upon completion.…”

Effect of Exhausted Coffee Ground Particle Size on Metal Ion Adsorption Rates and Capacities

“…The adsorption capacities of biosorbents derived from SCGs are influenced by how the material is prepared. Several SCG preparations have been reported including using SCGs as is, ,,,, rinsing with water, ,, modifying with an acid or a base, ,, or pyrolyzing to form activated carbon. ,,, In this study, ECGs were prepared by washing SCGs under alkaline conditions to remove soluble organic compounds that might have influenced any observed trends associated with adsorption rates or capacities due to changes in particle size. The adsorption capacities for each ion observed in this study were similar to values reported in the literature for coffee grounds used as is, washed with deionized water, or washed under alkaline conditions (Table ).…”

“…The adsorption capacities of biosorbents derived from SCGs are influenced by how the material is prepared. Several SCG preparations have been reported including using SCGs as is, 1 , 15 , 19 , 26 , 69 rinsing with water, 1 , 9 , 28 modifying with an acid or a base, 34 , 36 , 70 or pyrolyzing to form activated carbon. 39 , 43 , 71 , 72 In this study, ECGs were prepared by washing SCGs under alkaline conditions to remove soluble organic compounds that might have influenced any observed trends associated with adsorption rates or capacities due to changes in particle size.…”