Tannery industries’ effluent contains a high concentration of Cr (VI) which has the potential to affect the environment and public health. Therefore, this study aimed to investigate the optimization of Cr (VI) adsorption by activated carbon (AC) derived from Eichhornia crassipes from an aqueous solution. The adsorbent was activated with dilute sulfuric acid followed by thermal activation. AC was characterized using proximate analysis, SEM, FTIR, X-ray diffraction, and the BET method. The Cr (VI) removal optimization process was performed using a central composite design under the response surface methodology. The proximate analysis showed that the moisture content, volatile matter, ash content, and fixed carbon of the activated carbon were 5.6%, 18.2%, 14.4%, and 61.8% respectively. The surface areas of the Eichhornia crassipes before activation, after activation, and after adsorption were 60.6 g/m², 794.2 g/m², and 412.6 g/m² respectively. A highly porous structure with heterogeneous and irregular shapes was observed in the SEM micrograph. In the FTIR analysis, different peaks are indicated with various functional groups. The intensity of XRD peaks decreased as 2 theta values increased, which indicates the presence of an amorphous carbon arrangement. The point of zero charge (pH_pzc) of the activated carbon was found to be 5.20. A maximum Cr (VI) removal of 98.4% was achieved at pH 5, contact time 90 min, adsorbent dose 2 g, and initial Cr (VI) concentration of 2.25 mg/L. Statistically significant interactions (P < 0.05) were observed between the initial Cr (VI) concentration and adsorbent dose as well as the initial Cr (VI) concentration and contact time. Langmuir adsorption isotherm fitted the experimental data best, with an R² value of 0.99. The separation constant (RL) indicates that the adsorption process is favorable. The kinetic experimental data were best fitted with the pseudo-second-order model with an R² value of 0.99 whereas the adsorption rate is controlled by intraparticle and extragranular diffusion processes. Generally, the AC has the potential to be a strong adsorbent candidate for wastewater treatment at the industrial level.

The objective of this study is to investigate the adsorption performance of activated carbon derived from the leaves of Cordia africana for the removal of Cr (III) from an aqueous solution. The plant sample was collected, washed, dried, grounded, and sieved at 125μm mesh size. Adsorbent activation was done using H₃PO₄ at concentrations of 2585 and pyrolysis temperature of 400500°C. The activated carbon was characterized by proximate, SEM, BET, and FTIR analyses. A batch adsorption study was conducted to determine the effect of contact time, adsorbent dose, initial chromium concentration, and mixing speed on Cr (III) removal. The regeneration of the activated carbon was investigated by using 1M of HNO₃ as a desorbing solution for seven cycles. At optimum acid concentration and pyrolysis temperature, a surface area of 700m²/g was recorded. The moisture content, volatile matter, ash composition, fixed carbon, and bulk density of the activated carbon were found to be 5.3, 24.2, 6.2, 64.3, and 0.75g/mL, respectively. The SEM and FTIR analyses indicated that the surface morphology was full of cracks and different peaks were associated with plenty of functional groups, respectively. The maximum Cr (III) removal was attained at a contact time of 180min (89), adsorbent dose of 1.5g (54), initial concentration of 0.6g/L (47), and mixing speed of 300rpm (64). The equilibrium data were better described by Freundlich isotherm at R² value of 0.88, which implies that the adsorption process is conducted on a heterogeneous surface. The pseudo-first-order kinetics model with R² value of 0.99 best fits with the equilibrium data, which implies that physisorption controls the adsorption kinetics. Generally, it can be concluded that this locally prepared adsorbent is promising for the removal of chromium from industrial wastewater, but further factorial approach assessment has to be checked.

Rapid industrialization has significantly boosted economic growth but has also introduced severe environmental challenges, particularly in water pollution. This study evaluates the effectiveness of a nanocomposite composed of Rumex Abyssinicus Activated Carbon/Acid Activated Bentonite Clay/Graphene Oxide, and Iron Oxide (RAAC/AABC/GO/Fe₃O₄) for chromium removal from aqueous solutions. The preparation of the nanocomposite involved precise methods, and its characterization was performed using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, and the point of zero charge (pHpzc). Batch adsorption experiments were designed using Design Expert software with a central composite design under response surface methodology. The factors investigated included pH (3, 6, and 9), initial Cr (VI) concentration (40, 70, and 100 mg/L), adsorbent dose (0.5, 0.75, 1 g/200 mL), and contact time (60, 90, and 120 min). Adsorption isotherms were analyzed using nonlinearized Langmuir, Freundlich, and Temkin models, while pseudo-first-order and pseudo-second-order models were applied to adsorption kinetics. Characterization revealed a pHpzc of 8.25, a porous and heterogeneous surface (SEM), diverse functional groups (FTIR), an amorphous structure (XRD), and a significant surface area of 1201.23 m²/g (BET). The highest removal efficiency of 99.91% was achieved at pH 6, with an initial Cr (VI) concentration of 70 mg/L, a 90 min contact time, and an adsorbent dose of 1 g/200 mL. Optimization of the adsorption process identified optimal parameters as pH 5.84, initial Cr (VI) concentration of 88.94 mg/L, contact time of 60 min, and adsorbent dose of 0.52 g/200 mL. The Langmuir isotherm model, with an R² value of 0.92836, best described the adsorption process, indicating a monolayer adsorption mechanism. The pseudo-second-order kinetics model provided the best fit with an R² value of 0.988. Overall, the nanocomposite demonstrates significant potential as a cost-effective and environmentally friendly solution for chromium removal from wastewater.

Injera, a fermented staple food traditionally made from Teff flour, is a key part of the Ethiopian diet, with nearly all Ethiopians eating it at least once daily. Compositing various grain-based, and oilseed flours with Teff flour improves the nutritional content, and cost-effectiveness of the produced Injera. In Ethiopia, very limited studies were conducted to investigate the use of sorghum, rice, and teff flour blends combined with flaxseed flour in Injera preparation. Thus, this study was conducted to evaluate the anti-nutritional factors, microbiological characteristics, and ideal blending proportions of sorghum, rice, teff, and flaxseed flours to create a superior quality Injera via D-optimal design. One-way and two-way ANOVA, alongside Tukey’s pairwise comparison method, was employed to assess mean differences. The aim was to enhance the nutritional quality of Injera compared to a control sample made from 100% sorghum flour. The optimal nutritional profile was achieved with a blend comprising 50% sorghum, 20% rice, 30% teff, and supplemented with 3% flaxseed flour. This blend resulted in Injera containing 3.02% fiber, 9.30% protein, 83.16% carbohydrate, 393.24 kcal/100 g energy, 13.99 mg/100 g iron, 4.06 mg/100 g calcium, and 3.78 mg/100 g zinc. The optimization process identified this blend as optimal for improving the nutritional quality of Injera. The findings underscore that blending teff with sorghum, rice, and flaxseed flour enhances the nutritive value of Injera.

This study aimed to investigate the synthesis optimization of activated carbon-driven scrap tires for adsorbent yield and methylene blue removal under response surface methodology. The scrap tire sample was activated by KOH using ethanol as a solvent. The optimized activated carbon was characterized using proximate analysis, scanning electron microscope (SEM), X-ray diffraction (XRD), and Brunauer Emmett Teller (BET) method. The activated carbon was demineralized using 5M NaOH+ 98 H₂SO₄ (1:1) as a solvent to enhance the surface area. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were used to check the adsorption isotherm. The adsorption kinetics was checked using pseudo-first-order and pseudo-second-order models. Weber-Morris intraparticle diffusion model was used to study the diffusion mechanism. The optimum impregnation ratio, impregnation time, and carbonization temperature for synthesizing the activated carbon were 2g/g, 12hr, and 700C, respectively. The moisture content, volatile matter, ash content, fixed carbon, and bulk density of the activated carbon were 6.13, 9.42, 5.34, 79.11, and 0.89mg/L, respectively. The surface area of optimized activated carbon was enhanced by demineralization process and increased from 53m²/g to 260.26m²/g. Temkin adsorption isotherm with R² values of 0.982 and pseudo-second-order adsorption kinetics with R² values of 0.999 best fits the experimental data respectively. Intraparticle diffusion was not the only rate-controlling step for both optimized and demineralized (NaOH+H₂SO₄) activated carbon. It can be concluded that the optimized and demineralized activated carbon derived from scrap tires has a promising potential to be used as a low-cost adsorbent in developing countries including Ethiopia. However, further investigation needs to be conducted before scaling up at industrial level.