Natural fiber (NF) is one of the many resources that nature has provided. NFs decompose quickly and are biodegradable, renewable, and cost-effective. It may be scavenged from a variety of plant and animal sources. They are employed as reinforcing materials in polymers for NF composite development. Because of its environmental friendliness and long-term survivability, NF is growing in appeal among academics and researchers for usage in polymer composites. This study aims to offer a thorough evaluation of the most suitable and widely utilized natural fiber-reinforced polymer composites (NFPCs), along with their manufacture, processing, and applications. It also defines several external treatments of NF and their influence on the characteristics of NFPCs. The characteristics of NFPCs are affected by fiber supply, fiber type, and fiber structure. Numerous physical and chemical treatments were tested to see how they affected the thermal and strength properties of natural fiber-reinforced thermoplastic and thermosetting composites. Several polymer composite fabrication techniques were also studied. NFPCs have several disadvantages, notably low fire protection, poor strength properties, and greater moisture absorption, which have prevented their application. It is shown how NFPCs are employed in a variety of industries, particularly automotive and research industries. The review discovered that intentionally changing the regular fiber enhanced the thermochemical and physico-mechanical properties of the NFPCs by means of improving the grip between the fiber surface and the polymer framework. This study aims to provide important and fundamental facts on NF and their composites, which will aid in new investigations, the creation of a creative framework for polymer composite types, and the achievement of Sustainable Development Goals.

A new bioelectrochemical approach based on metabolic activities inoculated bacteria, and the microbial fuel cell (MFC) acts as biocatalysts for the natural conversion to energy of organic substrates. Among several factors, the organic substrate is the most critical challenge in MFC, which requires long-term stability. The utilization of unstable organic substrate directly affects the MFC performance, such as low energy generation. Similarly, the interaction and effect of the electrode with organic substrate are well discussed. The electrode-bacterial interaction is also another aspect after organic substrate in order to ensure the MFC performance. The conclusion is based on this literature view; the electrode content is also a significant challenge for MFCs with organic substrates in realistic applications. The current review discusses several commercial aspects of MFCs and their potential prospects. A durable organic substrate with an efficient electron transfer medium (anode electrode) is the modern necessity for this approach.

Given the increasing risks that antibiotic abuse poses to microecology and human health, it is imperative to develop incredibly powerful adsorbents. This study investigated the use of environmentally sustainable polymeric nanocomposite based on gum arabic (GA) and magnetic nanoparticles (MNPs) synthesized via co-precipitation method to form gum arabic magnetitic nanoparticles (GA-MNPs) as an efficient adsorbent for ciprofloxacin (CIP) removal from aqueous solution. The physicochemical properties and morphology of the synthesized GA-MNPs were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy Dispersive X-Ray Analysis (EDX). The experiment was designed by response surface methodology (RSM) and the Central Composite Design (CCD) was utilized to optimize the operating variables: contact time (0–120 min), pH (3–10), adsorbent dosage (0.10–0.40 g/L), and concentration of adsorbate (5–100 mg/L). Results showed that 96.30% was the maximum percentage of CIP removed. The adsorption effect of the CIP molecule on the surface of the GA-MNPs was investigated using regression analysis and analysis of variance. Furthermore, Freundlich Isotherm and Pseudo Second order kinetic equations have the highest consistency with experimental investigations suggesting double-layer adsorption. This implies that chemisorption was the mechanism involved. In addition, the calculated thermodynamic parameters were postulating an exothermic and spontaneous method in nature. Owing to its adsorption selectivity and recyclability, GA-MNPs could be classified as an environmentally friendly, less expensive, and highly efficient promising adsorbent for remediation of CIP from aqueous solution.

In this study poly (4-nitrophenylazo-3-aminopyridine - formaldehyde) (PNAAP-F) and poly (4-nitroarylazo-3-chloro-6-hydroxypyridine - formaldehyde) (NAACHP-F) were synthesized via diazotization, coupling and polycondensation reactions. The structural properties of the as-synthesized dyes were acquired using Fourier-transform infrared spectroscopy (FTIR) and UV-visible absorption maxima and their color, yield, melting point, solubility, and viscosity were determined via standard methods. UV-visible and FTIR results show successful formation of the polymeric dyes due to shift of wavelength of maximum absorption (λmax) (440-490 nm, 480-540 nm) and new absorption peak at around (2780-2995 cm-1) for methylene bridge respectively. The dyes were found to be of good yield (monomeric: 73.3%-87.2 %, polymeric: 53.8%-76.6 %), low melting point (monomeric: 112.6-121.2, and 136.0-137.0 °C, while polymeric: 134.0-144.5, and 149.4-154.7 °C), soluble in some solvents. The dyeing activity was carried out and assessed on nylon and polyester fabrics using the standard methods. The dyeing process was carried out via high temperature and carrier dyeing methods. The dyeing properties of the synthesized dyes were compared with those of commercial disperse dyes (terasil brilliant violet and terasil scarlet, brown). The dyeings of nylon and polyester had a very attractive hue and the color ranges from yellow and deep yellow shades with very good to excellent fastness to light, washing, hot pressing, and rubbing.

A potential and developing green technology for producing renewable energy and treating wastewater is the microbial fuel cell (MFC). Despite several advancements, there are still several serious problems with this approach. In the present work, we addressed the problem of the organic substrate in MFC, which is necessary for the degradation of metal ions in conjunction with the production of energy. The utilization of fruit waste as a carbon source was strongly suggested in earlier research. Hence, the mango peel was used as a substrate in the current study. Within 25days of operation, a 102-mV voltage was achieved in 13days, while the degradation efficiency of Cr³⁺ was 69.21, Co²⁺ was 72, and Ni²⁺ was 70.11. The procedure is carried out in the batch mode, and there is no continuous feeding of the organic substrate. In addition, a detailed explanation of the hypothesized mechanism for this investigation is provided, which focuses on the process of metal ion degradation. Lastly, future and concluding remarks are also enclosed.

Microbial fuel cell (MFC) is a new and interesting technology that can be used to treat wastewater without using electricity. The current research focuses on electron generation, which is one of the techniques major challenges. According to the latest literature, the study was planned to successfully remove the metals from artificial wastewater at high concentrations and generate electricity. On average, after 18days of operation, it offered 610mV with 1000 constant external resistance. The internal resistance was found to be 520. The achieved power density was 3.164mW/m² at an external resistance of 1000. The achieved removal efficiencies of Pb²⁺, Cd²⁺, Cr³⁺, and Ni²⁺ were 83.67, 84.10, 84.55, and 95.99, respectively. The operation lasted for 25days. The cyclic voltameter studies show that there is a gradual oxidation rate of organic substances, while on day 25, the removal efficiency reached its maximum. The specific capacitance was found to be high between days 15 and 20, i.e., 0.0000540F/g. It also indicated that biofilm was stable around day 18. Furthermore, the biological characterization also demonstrated that MFC operation was very smooth throughout the process, even at high concentrations (100mg/L) of metal ions. Finally, there is the MFC method, as well as some new challenges and future recommendations.