The growing demand for sustainable, high-performance materials has driven the development of natural fiber-reinforced polymers incorporating waste-derived fillers. This study explores the enhancement of sisal fiber-reinforced polyester composites using locally sourced bagasse ash (BA) and granite particles (GP) as single and hybrid fillers. Composites with a fixed 30% sisal content and varying filler loadings (4%, 8%, 12%), including hybrid mixtures (8% total), were fabricated via hand layup and systematically evaluated for mechanical performance and water absorption. This work presents a novel hybrid filler strategy using bagasse ash and granite waste in sisal–polyester composites. Results unequivocally demonstrated that adding these waste-derived fillers significantly improved both the mechanical performance and water absorption resistance compared to the unfilled composite. Specifically, composites reinforced with 8% GP achieved superior physical and static mechanical properties, showing optimal water absorption of 4.2% (vs. 8.12%), a maximum flexural strength of 51.57 MPa (vs. 34.63 MPa), and a compressive strength of 66 MPa (vs. 46 MPa). Conversely, the bio-filler proved optimal for toughness: 4% BA composites displayed the highest impact strength of 42 kJ/m², representing a 110% increase over the unfilled sample, while 8% BA yielded the maximum tensile strength of 40.5 MPa, representing a 62% improvement. These substantial enhancements are primarily attributed to improved interfacial adhesion and effective stress transfer among the matrix, fibers, and fillers, successfully mitigating failure initiation and boosting the overall composite performance. Owing to their improved mechanical properties and reduced water absorption, the developed composites show strong potential for use in wall-partition panels, insulation boards, and interior automotive components. This study demonstrates how agro-industrial waste fillers can be strategically selected or hybridized to tailor the mechanical and physical performance of natural fiber composites. Graphical abstract

The fast nutrient release behavior of chemical fertilizer is becoming a pressing issue in the environment and causes a decrease in agricultural land productivity. This study presents the development of slow-release urea fertilizer (SRUF) using bentonite-starch coating materials as a response to the weak utilization efficiency of conventional urea fertilizer. Production and characterization of SRUF have been carried out using bentonite-starch coating materials at different combination stages. The two-way ANOVA without replication was examined using Microsoft Excel for statistical data analysis to see the significance of the effect of affecting parameters on the response parameters. The SRUF product sample was characterized in terms of water swelling capacity, water retention capacity, strength, and nutrient release in static water. The result has shown, water swelling (%WS) to be in the range of (55.1–89.7%), water retention (%WR) (4.45–93.2%), crushing strength (87.74–99.02%), and nutrient release in static water (8.92-89.00%). The effect of bentonite, starch, and urea particle size on the quality of the SRUF has been discussed in this research study. ANOVA analysis showed that affecting parameters had a significant effect on the response parameters (P value < 0.05). From the experiment carried out, the SRUF sample with 25% bentonite and 10% starch achieved a better-quality product. Additionally, the SRUF sample was subjected to the SEM and FT-IR analysis and revealed, the produced SRUF sample has a better water and nutrient retaining behavior. Generally, the study demonstrates the efficiency of bentonite clay and starch for urea fertilizer coating purposes, and the materials were found to be the best candidates for coating purposes to solve problems associated with the use of chemical fertilizers.

Hexavalent chromium (Cr(VI)) is a highly toxic and carcinogenic pollutant widely discharged from tannery industries and poses serious environmental and public health risks when released into aquatic ecosystems. In this study, a sustainable and low-cost approach was developed for the efficient removal of Cr(VI) from real tannery wastewater using carbonized chicken eggshell, a readily available biowaste material. Eggshells were carbonized at 800 °C for 2 h, yielding a material with improved physicochemical properties and a surface area of 68.01 m²/g. The material was characterized using FTIR, XRD, proximate analysis, and BET surface area analysis. Optimization of adsorption parameters was conducted using Response Surface Methodology with a Central Composite Design employed to statistically evaluate the individual and interactive effects of key adsorption parameters. The developed quadratic model showed high statistical significance (P < 0.0001, R² = 0.9776). The effects of pH, adsorbent dosage, initial Cr(VI) concentration, and contact time were systematically evaluated. The optimal conditions for maximum Cr(VI) removal (99.63%) were pH 7, adsorbent dose 1.5 g, initial concentration 80 mg/L, and contact time 120 min. Adsorption data were best described by the Langmuir isotherm model (R² = 0.990), indicating monolayer adsorption, while kinetic studies followed the pseudo-second-order model (R² = 0.993), suggesting chemisorption. This study demonstrates the effective application of carbonized eggshells for Cr⁶⁺ removal from tannery wastewater, offering a cost-effective, eco-friendly solution for industrial effluent treatment.

The increasing industrial use of chromium, particularly in the textile sector, presents significant environmental challenges due to the improper disposal of chromium-laden wastewater. This study explores the potential of corncob-derived activated carbon as an effective adsorbent for removing hexavalent chromium (Cr (VI)) from wastewater generated by the MAA Garment Textile Factory in Mekelle, Ethiopia. Corncobs were collected from nearby agricultural fields in Quiha, Mekelle. They were then crushed using an electric grinder to a particle size of less than 100 mesh, followed by carbonization in a furnace at a temperature of 500 ℃. A comprehensive analysis of corncob revealed a moisture content of 7.95%, volatile matter at 75.24%, and an elemental composition of 51.21% carbon, 5.49% hydrogen, 0.3% nitrogen, and 43% oxygen. The functional groups of the activated carbon, chemically activated with potassium hydroxide, were analyzed using FTIR spectroscopy. Experimental results demonstrated a remarkable chromium removal efficiency of 99.45% within 75 minutes at a pH of 6.5 and a dosage of 0.175 grams, with an equilibrium adsorption capacity of 7.67 mg/g. The adsorption characteristics were effectively modeled using the Langmuir isotherm, indicating a maximum adsorption capacity of 515.5 mg/g under optimal conditions, with both pseudo-second-order kinetics and Langmuir model (R² = 0.999) accurately describing the process. This research underscores the feasibility of utilizing agricultural waste for chromium recovery, contributing to environmental management and resource conservation while promoting sustainable industrial practices in Ethiopia and beyond. Future studies should focus on scaling these methods for broader application across various industries to enhance environmental sustainability.