C — Journal of Carbon Research

In this work, sustainable aluminum-modified orange peels functionalized with graphene oxide (OP-Al-GO) were synthesized and evaluated for the removal of Methylene Violet (MV) and Reactive Red 120 (RR120) from aqueous solutions. Adsorption performance was systematically investigated in single-dye systems, binary dye mixtures, and real textile wastewater samples, and compared with that of orange peels (OP), orange peel–aluminum composite (OP-Al), and graphene oxide (GO). pH_pzc analysis clarified the surface charge of the adsorbent, while SEM and FTIR showed that the incorporation of aluminum and GO increased roughness and functional groups appearance, enhancing dye adsorption and confirming successful interactions. The OP-Al-GO composites exhibited improved removal efficiency for both dyes (64.8% for RR120 and 96.2% for MV) at pH 3.0. The presence of aluminum improved structural stability and surface charge regulation, while graphene oxide contributed to multiple adsorption mechanisms, including electrostatic attraction and π–π interactions. The adsorption kinetics were found to follow a pseudo-second-order (PSO) kinetic model for RR120 and an intraparticle-diffusion model (IPD) for MV, while isotherm analysis revealed a Langmuir behavior for MV and a Freundlich behavior for RR120. Langmuir maximum adsorption capacities were 298.7 and 10.8 mg/g for MV and RR120, respectively. High removal efficiency was maintained in binary dye mixtures, with OP-Al-GO achieving 96.9% removal of MV and 85.7% of RR120. Furthermore, the proposed adsorbent was tested on real wastewater samples, and the results highlight that the proposed adsorbents are promising, low-cost, and environmentally sustainable for textile wastewater treatment.

Conventional carbon-based electrodes like graphene are limited by costly, energy-intensive synthesis that rely on non-renewable precursors, challenging their scalability. While biomass-derived carbons (biochar) are a promising green alternative, achieving state-of-the-art performance typically requires chemical activation. Developing high-performance biochar through simple, scalable, and green pathways therefore remains a key challenge. In this work, we present a comprehensive physicochemical characterization of activation-free biochar derived from walnut, carob, rice husk and coffee via simple pyrolysis. Surface area, porosity and structural disorder were systematically analyzed to identify the key parameters governing ion interaction and charge storage. The results reveal a strong dependence of biochar properties on biomass type, with pronounced differences in accessible porosity and defect density. Among the materials studied, walnut-derived biochar combined a high specific surface area (1146 m²/g) with a high degree of structural disorder, highlighting the critical role of defects in enhancing ion adsorption and charge-transfer processes. Electrochemical measurements illustrated the functional implications of these intrinsic characteristics. Overall, this work demonstrates that carefully selected, unprocessed biomass can serve as a direct, low-cost source of functional carbon electrodes, providing insight into the parameters that dictate their electrochemical behavior and enable broader functional potential.

The strengthening of reinforced concrete (RC) beams requires repair systems that can enhance strength, stiffness, and energy dissipation without significantly increasing self-weight or compromising durability. This study explores the structural response of RC beams strengthened using an integrated shear–flexure system combining near-surface-mounted carbon fiber-reinforced polymer (NSM-CFRP) ropes and steel-reinforced geopolymer overlays in the compression zone. Monotonic three-point bending tests were performed on two RC beam specimens, one unstrengthened control and one strengthened beam, to obtain preliminary observations of load–deflection behavior, stiffness, ductility, and energy absorption. The strengthened specimen exhibited increases in ultimate load (28.6%), stiffness (13.6%), and energy absorption (7.65%) relative to the control beam, suggesting the potential for effective composite action between the CFRP ropes and geopolymer material. A three-dimensional nonlinear finite element model was developed using ATENA to support interpretation of the experimental response, incorporating detailed constitutive models for concrete, steel reinforcement, and CFRP ropes. The numerical predictions showed reasonable agreement with the experimental results. Within the limitations of the test matrix, the results indicate that the proposed dual strengthening system may offer a viable and sustainable approach for enhancing the shear–flexural performance of RC beams.