Mesoporous-rich calcium and potassium-activated carbons prepared from degreased spent coffee grounds for efficient removal of MnO4 2- in aqueous media.

Commercial ACs typically possess high surface areas and high microporosity. However, ACs with appreciable mesoporosity are growing in consideration and demand because they are beneficial for the adsorption of large species, such as heavy metal ions. Thus, in this study, degreased coffee grounds (DCG) were used as precursors for the production of ACs by means of chemical activation at 600 °C for the efficient removal of manganese in the form of MnO4 2-. One of the most common activating agents, ZnCl2, is replaced by benign and sustainable CaCl2 and K2CO3. Three ratios 1 : 1, 1 : 0.5 and 1 : 0.1 of precursor-to-activating agent (g g-1) were investigated. Porosimetry indicates 1 : 1 CaCl2 DCGAC is highly mesoporous (mesopore volume 0.469 cm3 g-1). CaCl2 DCGAC and K2CO3 DCGAC shows high adsorption capacities of 0.494 g g-1 and 0.423 g g-1, respectively for the uptake of MnO4 2- in aqueous media. The adsorption process follows pseudo-second order kinetics inline with the Freundlich isotherm (R 2 > 0.9). Thermodynamic data revealed negative values of ΔG (approx -0.1751 kJ mol-1) demonstrating that the adsorption process on 1 : 1 CaCl2DCGAC was spontaneous.

Superior Mesoporosity of Lipid-Free Spent Coffee Ground Residues.

As part of the biorefinery concept for spent coffee grounds (SCG), production of activated carbon (AC) was investigated from the degreased coffee grounds (DCG) left behind after oil extraction (primarily for biodiesel). The oils were extracted through conventional solvent extraction with GC/GC-MS confirming the oil was comparable to oils produced industrially. More significantly, analysis showed the DCG AC to have a four-fold increase in mesoporosity compared with the SCG AC with mesopore volumes of 0.6 and 0.15 cm3 g-1 , respectively. Adsorption trials showed a ten-fold increase in capacity for AuIII from 8.7 to 88.6 mg g-1 with subsequent experiments confirming that DCG AC displayed standard behavior for mesoporous materials of increasing adsorption capacity with decreasing pH. This raises the potential for valorization of SCG into a functional material for water remediation without the need for templating agents or expansion pretreatments with the added bonus of an additional material being produced simultaneously.

Valorisation of Biowastes for the Production of Green Materials Using Chemical Methods.

With crude oil reserves dwindling, the hunt for a sustainable alternative feedstock for fuels and materials for our society continues to expand. The biorefinery concept has enjoyed both a surge in popularity and also vocal opposition to the idea of diverting food-grade land and crops for this purpose. The idea of using the inevitable wastes arising from biomass processing, particularly farming and food production, is, therefore, gaining more attention as the feedstock for the biorefinery. For the three main components of biomass-carbohydrates, lipids, and proteins-there are long-established processes for using some of these by-products. However, the recent advances in chemical technologies are expanding both the feedstocks available for processing and the products that be obtained. Herein, this review presents some of the more recent developments in processing these molecules for green materials, as well as case studies that bring these technologies and materials together into final products for applied usage.