Study of the Active Carbon from Used Coffee Grounds as the Active Material for a High-Temperature Stable Supercapacitor with Ionic-Liquid Electrolyte

The adsorption of chlorpyrifos and malathion under environmentally relevant conditions using biowaste carbon materials

Water bodies face persistent contamination from organophosphorus pesticides like chlorpyrifos and malathion, which pose substantial environmental and health hazards due to their toxicity and resilience in ecosystems. This study explores the potential of spent coffee grounds, a common agricultural byproduct, as an eco-friendly adsorbent for eliminating these pesticides from polluted water. Spent coffee grounds underwent carbonization at 400 °C and various activation treatments using KOH, H3PO4, CO2, and their combinations. The impact of these activation methods on the adsorption capacity of carbonized materials was assessed under environmentally relevant conditions (25 °C, pH=6, and typical pesticide concentrations in wastewater). Results revealed that the physical and chemical properties of biowaste-derived materials significantly influence their adsorption efficiency, with KOH-activated adsorbents exhibiting the highest capacities ((16.1 ± 0.8) mg g-1 for chlorpyrifos and (11.2 ± 0.2) mg g-1 for malathion). Spent coffee grounds carbonized at 400 °C without additional activation demonstrated similar adsorption performance to the best-performing material ((19.4 ± 0.4) mg g-1 for chlorpyrifos and (10.6 ± 0.4) mg g-1 for malathion), with notably lower economic and environmental costs. Given its straightforward preparation and significant adsorption capacity, this material stands out as a sustainable solution for treating agrochemical wastewater containing chlorpyrifos and malathion.

A portable electrochemical immunosensor for ovarian cancer uses hierarchical microporous carbon material from waste coffee grounds

A simple label-free electrochemical immunosensor for ovarian cancer (OC) detection was developed using a hierarchical microporous carbon material fabricated from waste coffee grounds (WCG). The analysis method exploited near-field communication (NFC) and a smartphone-based potentiostat. Waste coffee grounds were pyrolyzed with potassium hydroxide and used to modify a screen-printed electrode. The modified screen-printed electrode was decorated with gold nanoparticles (AuNPs) to capture a specific antibody. The modification and immobilization processes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The sensor had an effective dynamic range of 0.5 to 50.0 U mL^-1 of cancer antigen 125 (CA125) tumor marker with a correlation coefficient of 0.9995. The limit of detection (LOD) was 0.4 U mL^-1. A comparison of the results obtained from human serum analysis with the proposed immunosensor and the results obtained from the clinical method confirmed the accuracy and precision of the proposed immunosensor.

Reusing Waste Coffee Grounds as Electrode Materials: Recent Advances and Future Opportunities

Coffee industry produces more than eight million tons of waste coffee grounds (WCG) annually. These WCG contain caffeine, tannins, and polyphenols and can be of great environmental concern if not properly disposed of. On the other hand, components of WCG are mainly macromolecular cellulose and lignocellulose, which can be utilized as cheap carbon precursors. Accordingly, various forms of carbon materials have been reportedly synthesized from WCG, including activated carbon, mesoporous carbon, carbon nanosheets, carbon nanotubes, graphene sheet fibers (i.e., graphenated carbon nanotubes), and particle-like graphene. Upcycling of various biomass and/or waste into value-added functional materials is of growing significance to offer more sustainable solutions and enable circular economy. In this context, this review offers timely insight on the recent advances of WCG derived carbon as value-added electrode materials. As electrodes, they have shown to possess excellent electrochemical properties and found applications in capacitor/supercapacitor, batteries, electrochemical sensors, owing to their low cost, high electrical conductivity, polarization, and chemical stability. Collectively, these efforts could represent an environmentally friendly and circular economy approach, which could not only help solve the food waste issue, but also generate high performance carbon-based materials for many electrochemical applications.

Enhanced adsorption of NO onto activated carbon by gas pre-magnetization

The NO removal efficiency was relatively low in the traditional activated carbon adsorption process. In this work, a gas pre-magnetization and activated carbon adsorption process was developed to enhance the adsorption of NO onto activated carbon. In this innovative and green process, the mixed gas was magnetized in the external magnetic field and then absorbed by activated carbon. The results indicated that the maximal removal rate of NO could be increased from 75.0% to 89.5%, and the NO adsorption capacity of commercial activated carbon in one hour elevated from 2.28 to 2.60 mg/g when the magnetic induction intensity of external magnetic field increased from 0 T to 2 T. The strengthening mechanism of the gas pre-magnetization was investigated. It was found that magnetic field could elevate the oxidation rate of NO by 11.4% and thus promote the physical adsorption of NO onto activated carbon. External magnetic field could increase the reaction activity of NO and promote the chemical reaction between NO and some functional groups (CO, CO and COOH) on the activated carbon and thus promote the chemisorption process of NO.

Achieving Good Temperature Stability of Dielectric Constant by Constructing Composition Gradient in (Pb1-x,Lax)(Zr0.65,Ti0.35)O3 Multilayer Thin Films

Ferroelectrics with a high dielectric constant are ideal materials for the fabrication of miniaturized and integrated electronic devices. However, the dielectric constant of ferroelectrics varies significantly with the change of temperature, which is detrimental to the working stability of electronic devices. This work demonstrates a new strategy to design a ferroelectric dielectric with a high temperature stability, that is, the design of a multilayer relaxor ferroelectric thin film with a composition gradient. As a result, the fabricated up-graded (Pb,La)(Zr_0.65,Ti_0.35)O₃ multilayer thin film showed a superior temperature stability of the dielectric constant, with variation less than 7% in the temperature range from 30 °C to 200 °C, and more importantly, the variation was less than 2.5% in the temperature range from 75 °C to 200 °C. This work not only develops a dielectric material with superior temperature stability, but also demonstrates a promising method to enhance the temperature stability of ferroelectrics.

Biomass Porous Carbons Derived from Banana Peel Waste as Sustainable Anodes for Lithium-Ion Batteries

Disordered carbons derived from banana peel waste (BPW) were successfully obtained by employing a simple one-step activation/carbonization method. Different instrumental techniques were used to characterize the structural, morphological, and textural properties of the materials, including X-ray diffraction, thermogravimetric analysis, porosimetry and scanning electron microscopy with energy-dispersive X-ray spectroscopy. The chemical activation with different porogens (zinc chloride, potassium hydroxide and phosphoric acid) could be used to develop functional carbonaceous structures with high specific surface areas and significant quantities of pores. The BPW@H3PO4 carbon exhibited a high specific surface area (815 m2 g-1), chemical stability and good conductivity for use as an anode in lithium-ion batteries. After 200 cycles, this carbon delivered a reversible capacity of 272 mAh g-1 at 0.2 C, showing a notable retention capacity and good cycling performance even at high current densities, demonstrating its effectiveness and sustainability as an anode material for high-energy applications in Li-ion batteries.

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.

Improving EDLC Device Performance Constructed from Plasticized Magnesium Ion Conducting Chitosan Based Polymer Electrolytes via Metal Complex Dispersion

The current work shows the preparation of plasticized chitosan-magnesium acetate Mg(CH3COO)2-based polymer electrolyte dispersed with nickel (Ni) metal complexes via solution casting. Investigations of electrical and electrochemical properties of the prepared polymer composite electrolyte were carried out. The structural and optical properties of the samples were studied using X-ray diffraction (XRD) and UV-Vis spectroscopy techniques. The structural and optical outcomes revealed a clear enhancement in both absorbance and amorphous nature of the samples upon the addition of Ni metal complexes. Through the simulation of impedance data, various ion transport parameters were calculated. The electrochemical performance of the sample was examined by means of transference number measurement (TNM), linear sweep voltammetry (LSV) and cyclic voltammetry (CV) measurements. The TNM analysis confirmed the dominance of ions as the main charge carrier in the electrolyte with tion of (0.96) compared to only (0.04) for tel. The present electrolyte was stable in the range of 0 V to 2.4 V, which was obtained from linear sweep voltammetry (LSV). A result from CV proved that the electrical double-layer capacitor (EDLC) has a capacitive behavior as no redox peaks could be observed. The presence of Ni improved the charge-discharge cycle of the EDLC due to its amorphous behavior. The average performances of the EDLC were recorded as 41.7 F/g, 95%, 5.86 Wh/kg and 628 W/kg for specific capacitance, coulombic efficiency, energy and power densities, respectively. The fabricated EDLC device was found to be stable up to 1000 cycles.