Activated carbon derived from waste coffee grounds for stable methane storage

Continuum Modeling with Functional Lennard-Jones Parameters for Methane Storage inside Various Carbon Nanostructures

Methane capture and storage are of particular importance for the development of new technology to reduce the effects of climate change and global warming. Carbon-based nanomaterials are among several porous nanomaterials proposed as potential candidates for methane storage. In this paper, we adopt a new continuum approach with functional Lennard-Jones parameters to provide interaction energies for methane inside carbon nanostructures, namely fullerenes, nanotube bundles, and nanocones. This study provides a significant improvement to previous continuum modeling approaches using the Lennard-Jones potential.

Surface and chemical characteristics of platinum modified activated carbon electrodes and their electrochemical performance

Platinum (Pt) loaded activated carbons (ACs) were synthesized by the thermal decomposition of platinum (II) acetylacetonate (Pt(acac)2) over chemically activated glucose-based biochar. The effect of Pt loading on surface area, pore characteristics, surface chemistry, chemical structure, and surface morphology were determined by various techniques. XPS studies proved the presence of metallic Pt0 on the AC surface. The graphitization degree of Pt loaded ACs were increased with the loaded Pt0 amount. The electrochemical performance of the Pt-loaded ACs (Pt@AC) was determined not only by the conventional three-electrode system but also by packaged supercapacitors in CR2032 casings. The capacitive performance of Pt@AC electrodes was investigated via cyclic voltammetry (CV), galvanostatic charge-discharge curves (GCD), and impedance spectroscopy (EIS). It was found that the Pt loading increased the specific capacitance from 51 F/g to 100 F/g. The ESR drop of the packaged cell decreased with the Pt loading due to the fast flow of charge through the conductive pathways. The results showed that the surface chemistry is more dominant than the surface area for determining the capacitive performance of Pt loaded AC-based packaged supercapacitors.

Novel Correlations between Spectroscopic and Morphological Properties of Activated Carbons from Waste Coffee Grounds

Massive quantities of spent coffee grounds (SCGs) are generated by users around the world. Different processes have been proposed for SCG valorization, including pyrolytic processes to achieve carbonaceous materials. Here, we report the preparation of activated carbons through pyrolytic processes carried out under different experimental conditions and in the presence of various porosity activators. Textural and chemical characterization of the obtained carbons have been achieved through Brunauer–Emmett–Teller (BET), ESEM, 13C solid state NMR, XPS, XRD, thermogravimetric and spectroscopic determinations. The aim of the paper is to relate these data to the preparation method, evaluating the correlation between the spectroscopic data and the physical and textural properties, also in comparison with the corresponding data obtained for three commercial activated carbons used in industrial adsorption processes. Some correlations have been observed between the Raman and XPS data.

Preparation of Activated Carbons from Spent Coffee Grounds and Coffee Parchment and Assessment of Their Adsorbent Efficiency

The valorization of coffee wastes through modification to activated carbon has been considered as a low-cost adsorbent with prospective to compete with commercial carbons. So far, very few studies have referred to the valorization of coffee parchment into activated carbon. Moreover, low-cost and efficient activation methods need to be more investigated. The aim of this work was to prepare activated carbon from spent coffee grounds and parchment, and to assess their adsorption performance. The co-calcination processing with calcium carbonate was used to prepare the activated carbons, and their adsorption capacity for organic acids, phenolic compounds and proteins was evaluated. Both spent coffee grounds and parchment showed yields after the calcination and washing treatments of around 9.0%. The adsorption of lactic acid was found to be optimal at pH 2. The maximum adsorption capacity of lactic acid with standard commercial granular activated carbon was 73.78 mg/g, while the values of 32.33 and 14.73 mg/g were registered for the parchment and spent coffee grounds activated carbons, respectively. The Langmuir isotherm showed that lactic acid was adsorbed as a monolayer and distributed homogeneously on the surface. Around 50% of total phenols and protein content from coffee wastewater were adsorbed after treatment with the prepared activated carbons, while 44, 43, and up to 84% of hydrophobic compounds were removed using parchment, spent coffee grounds and commercial activated carbon, respectively; the adsorption efficiencies of hydrophilic compounds ranged between 13 and 48%. Finally, these results illustrate the potential valorization of coffee by-products parchment and spent coffee grounds into activated carbon and their use as low-cost adsorbent for the removal of organic compounds from aqueous solutions.

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.

Development of Rubber Seed Shell–Activated Carbon Using Impregnated Pyridinium-Based Ionic Liquid for Enhanced CO2 Adsorption

In this study, rubber seed shell was used for the production of activated carbon by chemical activation using an ionic liquid, [C4Py][Tf2N] as an activating agent. Sample RSS-IL 800 shows the highest specific surface area of 393.99 m2/g, a total pore volume of 0.206 cm3/g, and a micropore volume of 0.172 cm3/g. The performance of AC samples as an adsorbent for CO2 was also studied using a static volumetric technique evaluated at a temperature of 25 °C and 1 bar pressure. The CO2 adsorption capacity for sample RSS-IL 800 was 2.436 mmol/g, comparable with reported data from the previous study. Results also show that the CO2 adsorption capacity decreased at a higher temperature between 50 and 100 °C and increased at elevated pressure due to its exothermic behavior. The Langmuir model fits the adsorption data well, and the isosteric heat of adsorption proved that the physisorption process and exothermic behavior occur.

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 from Spent Coffee Grounds: A Good Competitor of Commercial Carbons for Water Decontamination

In the framework of the circular economy, spent coffee grounds were converted into powdered activated carbon by means of pyrolysis, using potassium hydroxide as the activating agent. Its adsorption capacity on a panel of phenolic compounds was compared with those of two commercial powdered activated carbons, after preliminary studies on organic dyes with different ionic properties, to assess the affinity between adsorbates and adsorbents. Pseudo-first-order and pseudo-second-order kinetic models were carried out, together with Freundlich and Langmuir isotherms. They were useful to calculate the breakthrough at 5%, 10%, and 50% of adsorption and the partition coefficients for the comparison of performance between different sorbent systems in a less biased manner (e.g., reducing bias associated with operational settings like sorbate concentration and sorbents dosage). The results showed that the removal efficiency for SCGs-AC was comparable with that of the commercial activated carbons with the highest partition coefficients for methylene blue (12,455 mg/g/μM, adsorption capacity = 179 mg/g) and 3-chlorophenol (81.53 mg/g/μM, adsorption capacity = 3765 mg/g). The lower efficiency in bromothymol blue and bisphenol-A adsorption was due to its different morphology and surface properties.

Biorefinery of spent coffee grounds waste: Viable pathway towards circular bioeconomy

The circular bioeconomy plan is an innovative research based scheme intended for augmenting the complete utilization and management of bio-based resources in a sustainable biorefinery route. Spent coffee grounds based biorefinery is the emerging aspect promoting circular bioeconomy. The sustainable circular bioeconomy by utilizing SCG is achieved by cascade approaches and the inclusion of many biorefinery approaches to obtain many bio-products. The maximum energy recovery can be obtained by process integration. The economic analysis of the biofuel production from SCG is dependent on the cost of raw material, transportation, the need of labor and energy, oil extraction operations and biofuel production. The inclusion of new products from already established product can minimize the investment cost when related to the production cost. A positive net present value can be achieved via SCG biorefinery which indicates the profitability of the process.

Structure-Property Relationships in Polyethylene-Based Composites Filled with Biochar Derived from Waste Coffee Grounds

In this work, biochar (BC) derived from spent coffee grounds has been incorporated into high density polyethylene (PE) through melt mixing. The influence of the filler content on the rheological and thermal behavior of the obtained composites was assessed. In particular, a rheological study was performed systematically using different flow fields, including linear and nonlinear dynamic shear flow, revealing that the dynamics of PE macromolecules in the composite materials are slowed down because of the confinement of the polymer chains onto the filler surface and/or within the BC porous structure. Oscillatory amplitude sweep tests indicated that composites show weak strain overshoot behavior in the nonlinear regime: This finding clearly proves the formation of weak structural complexes, which cause a retardation of the macromolecular chains dynamics. Furthermore, the embedded BC particles were able to improve the thermo-oxidative stability of PE-based composites, remarkably increasing the PE decomposition temperatures.

Waste Coffee Ground Biochar: A Material for Humidity Sensors

Worldwide consumption of coffee exceeds 11 billion tons/year. Used coffee grounds end up as landfill. However, the unique structural properties of its porous surface make coffee grounds popular for the adsorption of gaseous molecules. In the present work, we demonstrate the use of coffee grounds as a potential and cheap source for biochar carbon. The produced coffee ground biochar (CGB) was investigated as a sensing material for developing humidity sensors. CGB was fully characterized by using laser granulometry, X-ray diffraction (XRD), Raman spectroscopy, field emission-scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and the Brunnauer Emmett Teller (BET) technique in order to acquire a complete understanding of its structural and surface properties and composition. Subsequently humidity sensors were screen printed using an ink-containing CGB with polyvinyl butyral (PVB) acting as a temporary binder and ethylene glycol monobutyral ether, Emflow, as an organic vehicle so that the proper rheological characteristics were achieved. Screen-printed films were the heated at 300 °C in air. Humidity tests were performed under a flow of 1.7 L/min in the relative humidity range 0–100% at room temperature. The initial impedance of the film was 25.2 ± 0.15 MΩ which changes to 12.3 MΩ under 98% humidity exposure. A sensor response was observed above 20% relative humidity (RH). Both the response and recovery times were reasonably fast (less than 2 min).

Converting environmental risks to benefits by using spent coffee grounds (SCG) as a valuable resource

Coffee is perhaps one of the most vital ingredients in humans' daily life in modern world. However, this causes the production of million tons of relevant wastes, i.e., plastic cups, aluminum capsules, coffee chaff (silver skin), and spent coffee grounds (SCG), all thrown untreated into landfills. It is estimated that 1 kg of instant coffee generates around 2 kg of wet SCG; a relatively unique organic waste stream, with little to no contamination, separated directly in the source by the coffee shops. The produced waste has been under researchers' microscope as a useful feedstock for a number of promising applications. SCG is considered a valuable, nutrients rich source of bioactive compounds (e.g., phenolics, flavonoids, carotenoids, lipids, chlorogenic and protocatechuic acid, melanoidins, diterpenes, xanthines, vitamin precursors, etc.) and a useful resource material in other processes (e.g., soil improver and compost, heavy metals absorbent, biochar, biodiesel, pellets, cosmetics, food, and deodorization products). This paper aims to provide a holistic approach for the SCG waste management, highlighting a series of processes and applications in environmental solutions, food industry, and agricultural sector. Thus, the latest developments and approaches of SCG waste management are reviewed and discussed.

Porous carbon-based adsorption systems for natural gas (methane) storage

The use of gas fuel has considerable environmental advantages over traditional types of fuel based on petroleum products or fossil coal. The adsorption technology for methane (natural gas) uptake, storage and transportation can serve as a connecting link in gas supply to customers. The review considers characteristics of adsorption systems for methane storage. The key methods used for the synthesis of microporous carbon adsorbents based on various organic and inorganic carbon-containing compounds are described. Methods for increasing the efficiency of methane storage systems based on carbon adsorbents are analyzed. Theoretical approaches to optimization of the properties of methane – carbon adsorbent systems are discussed.

The bibliography includes 174 references.

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.