Chemical Activation of an Activated Carbon Prepared from Coffee Residue

Improving Spent Coffee Biochar for Effective Organic Contaminant Removal from Aqueous Media

The contamination of (waste)water with organic pollutants, such as pharmaceuticals and dyes, is drastically increasing. Their removal process presents several difficulties, and often activated carbon (AC) is used in a filtration step. While commercial AC is often based on fossil resources, in this study, we present a new approach toward biochar from spent coffee (SC). This new AC has considerably enhanced surface areas and porosities, making it suitable for wastewater treatment. Using MgCO3 as an activating agent, a biochar with a significantly enhanced surface area of ∼600 m2/g is produced in a simple but efficient manner. The resulting biochar is effective for the removal of a whole spectrum of organic pollutants in aqueous systems. The dyes methylene blue (MB) and methyl orange (MO), but also the pharmaceuticals diclofenac (DCF) and tetracycline (TET), as well as the xenoestrogen bisphenol A (BPA), are successfully removed by up to 100% from aqueous solutions with the new adsorbents. Removal efficiencies depend on the pH of the solutions. In contaminant mixtures, the biochar shows preferences for adsorption toward some compounds but still shows very high adsorption capacities for all contaminants.

Value-Added Products from Coffee Waste: A Review

Coffee waste is often viewed as a problem, but it can be converted into value-added products if managed with clean technologies and long-term waste management strategies. Several compounds, including lipids, lignin, cellulose and hemicelluloses, tannins, antioxidants, caffeine, polyphenols, carotenoids, flavonoids, and biofuel can be extracted or produced through recycling, recovery, or energy valorization. In this review, we will discuss the potential uses of by-products generated from the waste derived from coffee production, including coffee leaves and flowers from cultivation; coffee pulps, husks, and silverskin from coffee processing; and spent coffee grounds (SCGs) from post-consumption. The full utilization of these coffee by-products can be achieved by establishing suitable infrastructure and building networks between scientists, business organizations, and policymakers, thus reducing the economic and environmental burdens of coffee processing in a sustainable manner.

Highly Efficient Multisubstrate Agricultural Waste-Derived Activated Carbon for Enhanced CO2 Capture

Activated carbon (AC) made of single-substrate agricultural wastes is considered to be a suitable raw material for the production of low-cost adsorbents; however, the large-scale application of these materials is highly limited by their low efficiency, seasonal scarcity, poor stability, low surface area, and limited CO₂ adsorption performance. In this study, composite activated carbon (CAC) was prepared via controlled carbonization followed by chemical activation of four wastes (i.e., peanut shell, coffee husk, corn cob, and banana peel) at an appropriate weight ratio. The Na₂CO₃-activated CAC showed a higher surface area and valuable textural properties for CO₂ adsorption as compared with KOH- and NaOH-activated CAC. The CAC production parameters, including impregnation ratio, impregnation time, carbonization temperature, and time, were optimized in detail. The as-prepared CACs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy, N₂ adsorption-desorption isotherm, and iodine number analysis. The CAC produced at optimal conditions exhibited the highest CO₂ removal efficiency and adsorption capacity of 96.2% and 8.86 wt %, respectively, compared with the single-biomass-derived activated carbon. The enhanced CO₂ adsorption performance is due to the large surface area, a considerable extent of mesopores, and suitable pore width. The adsorbent in this study reveals a promising strategy for mitigating the CO₂ emission problems instead of more expensive and ineffective materials.

Removal of anti-inflammatory drugs using activated carbon from agro-industrial origin: current advances in kinetics, isotherms, and thermodynamic studies

Nonsteroidal anti-inflammatory drugs (NSAIDs) are highly consumed around the world and consequently found as emerging pollutants in water; they are found in concentrations up to µg L−1 making their removal a priority. In this matter, adsorption is an efficient alternative for drug removal, so using activated carbon (AC) as an adsorbent is a highly explored subject. The current interest is to obtain AC from waste, for example, those of agro-industrial origin, reducing this way the overall costs of the process. Although information regarding the use of AC from agro-industrial origin in the removal of NSAIDs is limited, an exclusive compilation is required to understand the state of the art to date. This work aims to update information related to the adsorption of ibuprofen, diclofenac, and naproxen on agro-industrial AC, and it is focused on the period 2016–2021. It highlights the characteristics of agro-industrial AC responsible for efficient adsorption. Recent adsorption studies, including kinetics, isotherms, and thermodynamics, are analyzed and compared. Progress on removing NSAIDs from real wastewater is also presented and finally proposed adsorption mechanisms and costs related to these removal processes.

Carbon Adsorbents from Spent Coffee for Removal of Methylene Blue and Methyl Orange from Water

Activated carbons (ACs) were prepared from dried spent coffee (SCD), a biological waste product, to produce adsorbents for methylene blue (MB) and methyl orange (MO) from aqueous solution. Pre-pyrolysis activation of SCD was achieved via treatment of the SCD with aqueous sodium hydroxide solutions at 90 °C. Pyrolysis of the pretreated SCD at 500 °C for 1 h produced powders with typical characteristics of AC suitable and effective for dye adsorption. As an alternative to the rather harsh base treatment, calcium carbonate powder, a very common and abundant resource, was also studied as an activator. Mixtures of SCD and CaCO₃ (1:1 w/w) yielded effective ACs for MO and MB removal upon pyrolysis needing only small amounts of AC to clear the solutions. A selectivity of the adsorption process toward anionic (MO) or cationic (MB) dyes was not observed.

Nano-Intermediate of Magnetite Nanoparticles Supported on Activated Carbon from Spent Coffee Grounds for Treatment of Wastewater from Oil Industry and Energy Production

This work focused on evaluating the adsorptive removal of crude oil using a nano-intermediate based on magnetite nanoparticles supported on activated carbon synthesized from spent coffee grounds and the subsequent catalytic oil decomposition to recover by-products and regenerate the support material. The magnetite nanoparticles were synthesized by the co-precipitation method and were used as active phases on prepared activated carbon. The amount of crude oil adsorbed was determined by adsorption isotherms. In addition, dynamic tests were performed on a packed bed to evaluate the efficiency of the removal process. Thermogravimetric analysis and mass spectrometry were used to evaluate the catalytic powder and the quantification of by-products. Contrasting the results with commercial carbon, the one synthesized from the coffee residue showed a greater affinity for the oil. Likewise, the adsorption capacity increased by doping activated carbon with magnetite nanoparticles, obtaining an efficiency greater than 10%. The crude oil decomposition was carried out successfully by thermal cracking, obtaining a 100% removal. The gas produced after decomposition contains light hydrocarbons such as C2H4 and CH4 and shows a decrease in polluting species such as CO and CO2, leading to greater environmental sustainability of the process.

Plasma jet assisted carbonization and activation of coffee ground waste

Activated carbon has been extensively utilized to adsorb pollutants generated by industrial activities. There have been many attempts to efficiently produce activated carbon from spent coffee grounds in the field of environmental technology. In this study, the feasibility of the novel production of activated carbon from coffee ground waste using a plasma jet was evaluated. A rotating gliding arc generator was designed that used an N₂ plasma jet for the carbonization process and a CO₂ plasma jet for the activation process. It was confirmed that the coffee ground waste could be carbonized and activated by the two plasma jets in the same reactor. The characteristics of the surface morphologies of the activated carbon samples varied depending on the plasma treatment conditions, such as the electric power of the plasma jet and the treatment time. The results implied that the adsorption capacity of the activated carbon could be optimized by regulating the pore size and distribution based on the plasma treatment conditions with regard to the molecular size of the target adsorbate.

Activated carbon as catalyst support: precursors, preparation, modification and characterization

The preparation of activated carbon materials is discussed along selected examples of precursor materials, of available production and modification methods and possible characterization techniques. We evaluate the preparation methods for activated carbon materials with respect to its use as catalyst support and identify important parameters for metal loading. The considered carbon sources include coal, wood, agricultural wastes or biomass as well as ionic liquids, deep eutectic solvents or precursor solutions. The preparation of the activated carbon usually involves pre-treatment steps followed by physical or chemical activation and application dependent modification. In addition, highly porous materials can also be produced by salt templating or ultrasonic spray pyrolysis as well as by microwave irradiation. The resulting activated carbon materials are characterized by a variety of techniques such as SEM, FTIR, nitrogen adsorption, Boehm titrations, adsorption of phenol, methylene blue and iodine, TPD, CHNS/O elemental analysis, EDX, XPS, XRD and TGA.

Phosphorus recovery from process waste water made by the hydrothermal carbonisation of spent coffee grounds

This study investigates the recovery of phosphorus from the process water obtained through hydrothermal carbonisation (HTC) of a 'wet' biomass waste, namely spent coffee grounds. HTC was shown to liberate more than 82% of the total phosphorus in the grounds in the form of dissolved ortho-phosphate. Nanofiltration was used to concentrate the inorganic nutrients of the HTC process water, achieving a mass concentration factor of 3.9 times. The natural stoichiometry of phosphorus, magnesium and ammoniacal nitrogen in the nanofiltration retentate was favourable for struvite precipitation. 92.8% of aqueous phosphorus was recovered as struvite through simple pH adjustment, yielding a total phosphorus recovery of 75% from the feedstock spent coffee grounds.

Sorption of carbendazim and linuron from aqueous solutions with activated carbon produced from spent coffee grounds: Equilibrium, kinetic and thermodynamic approach

Spent coffee grounds (SCG) have been used for the production of activated carbon (AC) by impregnation with different ratios of phosphoric acid at 600 °C, Xp (H₃PO₄/coffee): 3:1^30%, 4:1^30%, 3:1^50% and 4:1^50%. The obtained AC was characterized by BET, FTIR and SEM. BET surface area corresponds to 803.422 m² g^-1. The influences of the main parameters such as contact time, the pesticides initial concentration, adsorbent dose, pH and temperature on the efficiency of separation process were investigated during the batch operational mode. Results were modeled by adsorption isotherms: Langmuir, Freundlich and Temkin isotherms, which gave satisfactory correlation coefficients. The maximum adsorption capacities calculated from the Langmuir isotherms were 11.918 mg g^-1 for carbendazim and 5.834 mg g^-1 for linuron at room temperature. Adsorption kinetics of carbendazim and linuron have been studied by the pseudo-first-order, the pseudo-second-order and the intraparticle diffusion model. The results of adsorption kinetics have been fitted the best by pseudo-second-order model. The resulted data from FTIR characterization pointed to the presence of many functional groups on the AC surface. SCG adsorbent, as an eco-friendly and low-cost material, showed high potential for the removal of carbendazim and linuron from aqueous solutions.

Synthesis of activated carbon from peanut shell as dye adsorbents for wastewater treatment

In this study, the adsorption capacities of peanut shell activated carbon samples prepared using three types of peanut shell as raw material were compared. The effects of activation state, carbonization temperature, carbonization time, adsorption time during decolorization, and dosage on the performance of the peanut shell activated carbon samples were investigated. The performance of the modified peanut shell (activated carbon) on the decolorization of reactive brilliant blue X-BR and the adsorption kinetics were evaluated systematically. Among the three types of peanut shell activated carbon, the activated carbon that was first activated by phosphoric acid and then carbonized at 450°C for 3 h displayed the best performance, with an optimum dosage of 4 g l−1 and an optimum adsorption time of 2 h. The pseudo-second-order kinetics equation and the intraparticle diffusion equation could well describe the adsorption behavior of the activated carbon prepared by phosphoric acid activation. Intraparticle diffusion was not the only factor affecting the adsorption rate of the activated carbon on reactive brilliant blue X-BR.

A spent coffee grounds based biorefinery for the production of biofuels, biopolymers, antioxidants and biocomposites

Spent coffee grounds are composed of lipid, carbohydrates, carbonaceous, and nitrogen containing compounds among others. Using n-hexane and n-hexane/isopropanol mixture highest oil yield was achived during soxhlet extraction of oil from spent coffee grounds. Alternatively, supercritical carbon dioxide can be employed as a green solvent for the extraction of oil. Using advanced chemical and biotechnological methods, spent coffee grounds are converted to various biofuels such as, biodiesel, renewable diesel, bioethanol, bioethers, bio-oil, biochar, and biogas. The in-situ transesterification of spent coffee grounds was carried out in a large scale (4 kg), which led to 80-83% biodiesel yield. In addition, a large number of value added and diversified products viz. polyhydroxyalkanoates, biosorbent, activated carbon, polyol, polyurethane foam, carotenoid, phenolic antioxidants, and green composite are obtained from spent coffee grounds. The principles of circular economy are applied to develop a sustanaible biorefinery based on valorisation of spent coffee grounds.