Oxytetracycline Adsorption from Aqueous Solutions on Commercial and High-Temperature Modified Activated Carbons

The aim of the work was to evaluate the possibility of using commercial and modified activated carbons for the removal of oxytetracycline from aqueous solutions. The kinetics and statics of adsorption as well as the effect of the activated carbon dose and solution pH on the efficiency of the oxytetracycline adsorption were analyzed. Based on the study of oxytetracycline adsorption isotherms, the activated carbons were ranked in the following order: F-300 > WG-12 > Picabiol > ROW08 > WACC 8 × 30 > F-100 > WAZ 0.6–2.4. The most effective activated carbons were characterized by large specific surfaces. The best matching results were obtained for: Redlich–Peterson, Thot and Jovanovic models, and lower for the most frequently used Freundlich and Langmuir models. The adsorption proceeded better from solutions with pH = 6 than with pH = 3 and 10. Two ways of modifying activated carbon were also assessed. A proprietary method of activated carbon modification was proposed. It uses the heating of activated carbon as a result of current flow through its bed. Both carbons modified at 400 °C in the rotary kiln and on the proprietary SEOW (Joule-heat) modification stand enabled to obtain adsorbents with higher and comparable monolayer capacities. The advantage of the proposed modification method is low electricity consumption.

Enthalpic and Liquid-Phase Adsorption Study of Toluene–Cyclohexane and Toluene–Hexane Binary Systems on Modified Activated Carbons

The liquid-phase adsorption of toluene in cyclohexane and hexane solutions on modified activated carbons was evaluated; the energy involved in the interaction between these solutions and the solids was determined by immersion enthalpies of pure solvents and their mixtures, and the contribution of the system constituents was calculated by differential enthalpies. The thermal treatment generated modifications that favored adsorption and interaction with the evaluated solutions, since it increased the textural parameters and the basic character of the samples. Cyclohexane could create greater competition with the adsorption sites compared to hexane, but it favored the increase in adsorption capacities (0.416 to 1.026 mmol g−1) and the interactions with the solid evaluated through the immersion enthalpies. The immersion enthalpies of pure solvents (−16.36 to −112.7 J g−1) and mixtures (−25.65 to −104.34 J g−1) had exothermic behaviors that were decreasing due to the possible displacement of solvent molecules when increasing the solute concentration in the mixtures. The differential enthalpies for toluene were negative (−18.63 to −2.14 J), mainly due to the π–π interaction with the solid, while those of the solvent–solid component tended to be positive values (−4.25 to 55.97 J) due to the displacement of the solvent molecules by those of toluene.

Adsorption of CO Gas and Cigarette Smoke Using NiO-Modified Metal Activated Carbon

Smoking can cause various ongoing complications in the body. One of the dangerous components of cigarette smoke is carbon monoxide which is one of the most toxic pollutants produced from cigarette gas emissions. Reducing levels in the air can utilize the adsorbent in the form of activated carbon which has the capacity and selectivity to these pollutants. Activated carbon was prepared from corn stalks which were activated by KOH at 750 °C based on previous research. The activated carbon which produced have Iodine number equal to 602 mg/g and SBET reached 599 m2/g. To strengthen the adsorption power, the results of activated carbon will be modified by impregnation of NiO metal. Metal impregnation varied with loading percentage 0.5, 1 and 2%. Modified activated carbons were then characterized by the Iodine Number test, BET test, SEM test, and EDX test. Each of the modified activated carbon will be tested for the capacity and selectivity of adsorption of CO and cigarette smoke. The best modified activated carbon is Mod 0.5% with Iodine number equal to 844 mg/g and SBET reached 839 m2/g. The best adsorption ability is obtained by 0.5% NiO-modified activated carbon which able to reduce CO gas levels by 29.9% and for cigarette smoke reaching 82.16%.