Highly efficient adsorption of congo red and methyl orange dyes using mesoporous α-Mn2O3 nanoparticles synthesized with Pyracantha angustofolia fruit extract

Due to the many applications of manganese oxides in water treatment, this research aimed to synthesize α-Mn2O3 nanoparticles through a green method and investigate the dye adsorption capacity of them. The α-Mn2O3 nanoparticles were successfully synthesized using KMnO4 and aqueous extract of Pyracantha angustofolia fruits under hydrothermal conditions and calcination. The products were identified using Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM) analyses. The adsorption capacity of methyl orange (MO) and Congo red (CR) dyes were evaluated at different concentrations (25, 50, and 75 ppm) using α-Mn2O3 nanoparticles. Results revealed the spherical and porous structure of α-Mn2O3 nanoparticles with a specific surface area of 21.7 m2.g-1. Dye removal significantly increased with pH decrement. The adsorption capacity for MO and CR was 73.07 and 70.70 mg.g-1, respectively. The adsorption data of both dyes followed a pseudo-second-order kinetic model. The best fitted models for MO and CR adsorption were the Langmuir isotherm and the Dubinin-Radushkevich, respectively. In addition, a possible adsorption mechanism was proposed for both dyes. The findings showed that α-Mn2O3 nanoparticles are very efficient adsorbents for removing anionic dyes.

Acidified groundnut cake for enhanced bio adsorption of anionic textile dye Reactive Red 195

This study focuses on the improvement of bioremediation of textile dye Reactive Red 195 using agro-industrial waste, groundnut oil cake (GNOC) obtained after oil-pressing. The treatment of GNOC with 1 N H2SO4 had resulted in physiochemical changes on the insoluble porous adsorbent, which improved their adsorption efficiency. The dye removal efficiency increased from 55% to 94% on acidification of GNOC. The raw groundnut oil cake (RGNOC) and acid-treated groundnut oil cake (AGNOC) were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction, and zeta potential. The rate and efficiency of dye adsorption were examined using adsorption kinetics and isotherm models. The results confirm that acid-treated GNOC eliminates impurities, alter the surface functional groups, and significantly increase porous surface areas of RGNOC. The investigation of key factors such as contact time, initial concentration of dye, static/agitation impact, particle size, and adsorbent dose had significantly influenced adsorption capacity of GNOC. Adsorption of dye fits best into the Langmuir model and equilibrium data of dye on AGNOC was explained by psuedo-second-order reaction with maximum adsorption capacity of 12.65 mg/g. This emphasis AGNOC has a very excellent potential to remove the textile dye Reactive Red dye from industrial effluent.

Optimization and Modeling of Cr (VI) Removal from Tannery Wastewater onto Activated Carbon Prepared from Coffee Husk and Sulfuric Acid (H2SO4) as Activating Agent by Using Central Composite Design (CCD)

The primary goal of this research is to lower the hexavalent chromium (Cr (VI)) concentration that has occurred from the growth of the tannery industry. As a result, the potential for heavy metal concentration is increasing day by day. Industrial effluent containing Cr (VI) contributes significantly to water pollution. Chromium hexavalent ion (Cr (VI)) in wastewater is extremely hazardous to the environment. It is critical to address such a condition using activated carbon derived from biomass. Adsorption is one of the most successful methods for removing hexavalent chromium from wastewater. Treated wastewater has no substantial environmental contamination consequences. The ash content, moisture content, volatile matter content, and fixed carbon content of wet coffee husk were 3.51, 10.85, 68.33, and 17.31, respectively. The physicochemical properties of coffee husk-based activated carbon (CHBAC) obtained during experimentation were pH, porosity, the yield of CHBAC, bulk density, point of zero charges, and specific surface area of 5.2, 58.4 percent, 60.1 percent, 0.71 g/mL, 4.19, and 1396 m2/g, respectively, indicating that CHBAC has a higher capacity as an adsorbent medium. For optimization purposes, the parameters ranged from pH (0.3–3.7), dose (2.3–5.7) $g$ , and contact time (0.3–3.7) hr. The quadratic models were chosen for optimization, and the $p$ value for the model was significant since it was less than 0.05, but the lack of fit model was inconsequential because it was more than 0.05. The optimum adsorption obtained with numerical optimization of Cr (VI) was 97.65 percent. This was obtained at a pH of 1.926, a dose of 4.209 g/L, and a contact time of 2.101 hours. This result was observed at a pH of 1.93, a dosage of 4.2 g/L, and a contact duration of 2.1 hours. The desirability obtained during numerical optimization was 1. Coffee husk-based activated carbon has a bigger surface area, and it has a stronger ability to absorb hexavalent chromium from tannery wastewater effluents.

Preparation of zeolitic imidazolate framework-67/wool fabric and its adsorption capacity for reactive dyes

Zeolitic imidazolate framework-67 (ZIF-67) formed by Co²⁺ and 2-methylimidazole (MIM) is widely used for adsorption and separation of pollutants. However, there are some disadvantages for ZIF-67 powder, such as strong electrostatic interaction and difficulty in recovery from the liquid phase. The available way to solve the above problems is choosing a suitable substrate to load ZIF-67. The amino and hydroxyl of wool fabrics effectively capture and fix ZIF-67, making it easy to separate ZIF-67 by taking out the composite materials from aqueous solution. In this study, ZIF-67/Wool fabric (ZW) was successfully prepared. The results show that ZIF-67 has better adsorption performance for reactive dyes with more sulfonic groups, higher molecular weight and lower steric resistance. The equilibrium adsorption capacity of ZW for reactive red 195 was 4.15 mg g^-1. The adsorption accorded with pseudo-second-order kinetic model and Langmuir isotherm. This study improved the application of ZIF-67, which provided a treatment method for dyeing wastewater and made it possible to recycle waste wool.