To improve the ability of the rice husk to purify colored wastewater, effluent from the alkaline scouring of cotton yarn was used immediately after the scouring (without cooling and additionally added chemicals) in order to remove the non-cellulosic silicon-lignin shield from the rice husk’s surface. This rice husk, with 93.8 mg/g adsorption capacity, behaves similarly as the rice husk treated with an optimized alkaline scouring recipe consisting of 20 g/L NaOH, 2 mL/L Cotoblanc HTD-N and 1 mL/L Kemonecer NI at 70 °C for 30 min with an adsorption capacity of 88.9 mg/g of direct Congo red dye. Treating one form of waste (rice husk) with another (effluent from the alkaline scouring of cellulosic plant fibers), in an effort to produce a material able to purify colored effluent, is an elegant environment-friendly concept based on the circular economy strategy. This will result in a closed-loop energy-efficient process of the pre-treatment of cotton (alkaline scouring), modification of rice husk using effluent from the alkaline scouring, dyeing cotton fabrics and cleaning its colored effluents with modified rice husk without adding chemicals and energy for heating.
Abstract:The paper presents the results achieved during the process of nickel removal from aqueous solutions by adsorption on alumina (Aluminum oxide) in continuous conditions. The continuing experiments were conducted in a glass column with diameter of 16 mm and fi xed bed of adsorbent with quantity ranging from 30 to 115 g, adsorbent grains size from 1.0 to 2.0 mm, and retention time of 0.5 to 12 minutes. The quantity of nickel in the aqueous solutions was changed within the range of 0.045 up to 0.12 mg/l Ni. The analysis of the obtained experimental data defi ned the mutual affection of the retention time, the initial nickel concentration in the water, and the adsorbent quantity, i.e. the content of the adsorbent in the treated solution to the adsorbent capacity.According to the achieved results, logarithmic mathematical model showed best correlation between experimental and calculated values, also maximum nickel ions adsorption uptake onto the alumina were determined as 400 mg/g.
Adsorption of arsenites and arsenates from aqueous solutions by application of modified natural inorganic materials-a kinetic study Two commercially available adsorbents, white tuff from Strmos region and a material with a commercial name Zeofit obtained from Palanka region, were investigated as possible raw materials for adsorption of arsenites and arsenates from aqueous solutions. These raw materials were modified through chemical insertion of iron within the basic material structure and ionic substitution of calcium and magnesium ions with sodium ions in order to improve the sorptive and ion-exchange properties of studied raw materials. Obtained results from the experimental study of the adsorption of arsenic ions from simulated aqueous solutions suggest that the Zeofit material produced better results than the white tuff material, which showed satisfactory adsorption efficiency only at lower arsenic ions concentrations. Drinking water from the water supply system in Skopje was used for preparation of the studied arsenic ions solutions. Performed kinetic study and resulting kinetic models for both materials, generated a kinetic model of first order for the white tuff material, whereas the Zeofit material adsorption kinetics indicated a pseudosecond order.
Two raw materials were investigated to provide a cheap and effi cient arsenic removal from drinking water supply. For this purpose, studied materials were modifi ed by insertion of iron within the materials' structure and substitution of calcium and magnesium ions with sodium ions in order to improve the sorptive and ion-exchange properties. White tuff from Strmos region and the commercially available Zeofi t were the materials considered within our study. Simulations were performed on prepared solutions of arsenic added to water samples from the water supply in Skopje. Obtained results suggest that the Zeofi t material produced better results regarding arsenic adsorption at various initial arsenic concentrations. The white tuff from Strmos is effective only at lower initial concentrations of arsenic. Regarding the equilibrium study on investigated systems for both materials, implemented models produced a good fi t when applied to As 5+ systems. The Strmos material did not produce satisfactory fi tting results to implemented equilibrium models for the As 3+ systems.
Equilibrium, kinetic, thermodynamic aspects and mechanism of Congo red adsorption onto rice husk treated with effluent from cotton pre-treatment are examined by altering the initial dye concentration, contact time, temperature, and adsorbent mass. When a lower mass is applied, the treated rice husk adsorbs the Congo red following the Langmuir model, while at a higher mass, the adsorption follows the Freundlich model. А maximum of 149.1 mg/g Congo red is adsorbed with 10 g/L rice husk at 70oC. This capacity of the chemically modified rice husk is one of the better ones found in the literature. The calculated Dubinin–Radushkevich activation energy indicates the physical nature of Congo red adsorption adsorbed under the pseudo-second-order kinetic model. The thermodynamic analysis confirmed spontaneous and endothermic adsorption with physically created Congo red-rice husk bonds. These results showed the applicability of the circular economy concept in the effort to obtain an efficient adsorbent without wasting additional chemicals and energy that could be used to create a continuous column-mode process of rice husk modification and purification of colored effluent from the textile industry.
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