The aim and originality of our current study are to use the original biomass (activated carbon) obtained by functionalizing waste banana peels (commonly found in Turkey) with acid in NaBH4 methanolysis and to examine its contribution to the hydrogen generation rate (HGR). Our study consisted of three stages. In the first stage, the optimum conditions were determined by examining the catalyst under parameters such as different acid types, different carbonization temperatures, and different carbonization times. Thus, based on the maximum HGR value, the optimum conditions were determined as H3PO4, 600 °C, and 40 min. In the second step, the effects of parameters such as acid concentration, NaBH4 concentration, catalyst amount, and temperature on HGR were investigated. As a result of methanolysis experiments (condition: catalyst amount: 100 mg, acid amount: 30%, NaBH4 concentration: 2.5%, temperature: 30 °C, carbonization temperature: 400 °C, and carbonization time: 40 min.), the maximum HGR value, the reaction completion time and activation energy were found as 65,625 mLmin− 1gcat−1, 0.233 min, and 4.56 kJ/mol, respectively. It was observed that the obtained activation energy was lower than that of some catalysts available in the literature. In addition, the structural and morphological examination of the banana peel (catalyst) with high HGR and low activation energy revealed that the acid functionalization process was successfully carried out.

In this work, we report a direct preparation of a few-walled carbon nanotube (FWCNTs) and NiMgAl composites namely FWCNT-NiMgAl by pyrolysis of waste high-density polyethylene (HDPE) plastic at 800 °C with NiMgAl-layered double hydroxide (LDH) as catalysts. The composite formation is carried out in a single step using our lab-developed pyrolysis reactor. The NiMgAl-LDH catalyst was prepared by co-precipitation method and the FWCNTs were grown on the NiMgAl-LDH catalyst with FWCNT yield of 10% and FWCNT-NiMgAl composite yield of 55% whose quality is determined by Raman ID/IG ratio of 2.57. The average outer and inner diameter of the FWCNT are found to be 5.5 nm and 2.9 nm, respectively, from TEM and 2.92 nm from the outer RBM (radial breathing mode) band, which indicates the formation of a few-walled CNTs. FWCNT-NiMgAl is used for the fabrication of flexible supercapacitor electrodes on a polyethylene terephthalate (PET) sheet which achieved a specific capacitance of 432 Fg− 1 in a wide potential range (ΔV = 2) at a scan rate of 5 mV s− 1 in 2 M KOH electrolyte with a high energy density of 240 Wh kg− 1, whereas NiMgAl displayed a capacitance of 200 Fg− 1 with an energy density of 111 Wh kg− 1. The diffusion-type charge storage mechanism (pseudocapacitance) is found to be dominant with contributions of 73.2% and 69.75% for NiMgAl and FWCNT-NiMgAl, respectively. The highest specific capacitance and energy density are obtained for NiMgAl in 2 M KCl and for FWCNT-NiMgAl in 2 M NaOH electrolytes. However, the largest potential window is observed in KOH electrolyte for both NiMgAl and FWCNT-NiMgAl with value of ΔV = 2 V. The electrode material shows good stability in acidic electrolytes and also shows good capacitive stability at high frequencies maintaining a phase angle of 70°. The present work is a novel approach to fabricate low-cost multifunctional carbon composite nanomaterials and will contribute to the research on low-cost waste-derived CNT composite preparation and its application in flexible energy storage devices.

There is an ever growing interest in the development of biochar from a large variety of agrowastes. Herein, the main objective is the conversion of pomegranate peel powder biochar and its post-functionalization by phosphoric acid treatment, followed by arylation organic reaction. The latter was conducted using in situ-generated diazonium salts of 4-aminobenzoic acid ( H2N-C6H4-COOH), sulfanilic acid ( H2N-C6H4-SO3H) and Azure A dye. The effect of diazonium nature and concentration on the arylation process was monitored using thermal gravimetric analysis (TGA) and Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). SEM pictures showed micrometer-sized biochar particles with tubular structure having about 10–20 μm-wide channels. SEM studies have shown that arylation did not affect the morphology upon arylation. The porous structure did not collapse and withstood the arylation organic reaction in acid medium did not collapse upon arylation. TGA and Raman indicated gradual changes in the arylation of biochar at initial concentrations 10– 5, 10– 4 and 10– 3 mol L− 1 of 4-aminobenzoic acid. The detailed Raman spectra peak fittings indicate that the D/G peak intensity ratio leveled off at 3.35 for 4-aminobenzoic acid initial concentration of 10– 4 mol L− 1, and no more change was observed, even at higher aryl group mass loading. This is in line with formation of oligoaryl grafts rather than the grafting of new aryl groups directly to the biochar surface. Interestingly, Azure A diazonium salt induced much lower extent of surface modification, likely due to steric hindrance. To the very best of our knowledge, this is the first report on diazonium modification of agrowaste-derived biochar and opens new avenues for arylated biochar and its applications.

To solve the problem of water pollution, researchers have proposed a photocatalytic degradation technology, in which the key factor is the development of efficient photocatalytic materials. Graphitic carbon nitride (g-C3N4), an n-type semiconductor, has been widely studied due to its suitable band gap (2.7 eV), low cost, easy preparation, non-toxicity, and high photostability. However, the pure-phase g-C3N4 still has defects such as low specific surface area, insufficient visible light absorption, low charge mobility, few active sites for interfacial reaction, and easy recombination of photogenerated electron–hole pairs, which leads to the lower photocatalytic activity of g-C3N4. Aiming at the problems mentioned above, this paper focus on the synthesis of g-C3N4-based composites with high photocatalytic activity via lemon juice induction method. Thiourea and lemon juice were selected as precursors, and carbon quantum dots (CQDs) as electron mediators were introduced anchoring on the surface of g-C3N4 to build g-C3N4/CQDs with compact interface. The results showed that small-sized CQDs are uniformly distributed on the surface of g-C3N4, and the g-C3N4/CQDs composite has a 2D0D structure, which reduces the recombination of photogenerated electron–hole pairs. The photocatalytic degradation efficiency of 4% g-C3N4/CQDs for RhB reaches the highest data of 90.9%, and the photocatalytic degradation rate is 0.016 min− 1, which is about 2.3 times that of g-C3N4. After four cycles of photocatalytic reaction, the photocatalytic degradation efficiency of the material remained at 81.7%. Therefore, the g-C3N4/CQDs synthesized via lemon juice induction has a more stable microstructure, and the charge separation efficiency is greatly improved, which is suitable for practical photocatalytic environmental protection.

Antioxidants are food additives that extend the shelf life of food products by preventing lipid rancidity caused by active oxygen. They can either be naturally-derived or manufactured synthetically via chemical synthesis. In this study, method validation of five synthetic antioxidants, namely butylated hydroxyanisole, butylated hydroxytoluene, tertiary butylhydroquinone, propyl gallate, and disodium ethylenediaminetetraacetic acid, was performed using a high performance liquid chromatography–ultraviolet visible detector, and the method applicability was evaluated by analyzing foods containing antioxidants. The coefficient of determination (R2) average was 0.9997, while the limit of detection and limit of quantification were 0.02–0.53 and 0.07–1.61 mg/kg, respectively. The intra and inter-day accuracies and precisions were 83.2±0.7%–98.7±2.1% and 0.1%–5.7% RSD, respectively. Inter-laboratory validation for accuracy and precision was conducted using the Food Analysis Performance Assessment Scheme quality control material. The results satisfied the guidelines presented by the AOAC International. In addition, the expanded uncertainty was less than 16%, as recommended by CODEX. Consequently, to enhance public health safety, the results of this study can be used as basis data for evaluating the intake of synthetic antioxidants and assessing their risks in Korea.