RESUMO
This study searched for the best synthesis route for producing an adsorbent from the alkaline fusion of volcanic rock powder waste. The samples synthesized under different conditions of temperature and alkalizing ratio/precursor material, nine in total (NP.F, NP.F1, NP.F2, ...NP.F8 ), were used in the adsorption of acid green 16 (AG 16) and acid red 97 (AR 97) dyes and Ag+, Co2+, and Cu2+ ions. Subsequently, the 22 central composite rotational design (CCRD) was applied, and the effects of the alkalizing ratio (NaOH)/volcanic rock (VR) and temperature (T) on the synthesis process were analyzed in terms of their influence on the physical properties of the materials and in the process of adsorption of contaminants. From the experimental design, it can be seen that the independent variables alkalizing ratio/volcanic rock and temperature greatly influence the characteristic and synthesis of adsorbent materials by alkaline fusion, which in turn reflects on the results achieved in the adsorption of contaminants. Therefore, the temperature of 550 °C and NaOH/VR ratio equal to 1 was the most satisfactory synthesis route to obtain high values of adsorption capacity (q, mg g-1) and removal (R, %) for all studied contaminants, as well as the optimization of the physical characteristics of the material. For example, the adsorption capacity of dye AG 16 was 49.1 mg g-1, and for Ag+ was 66.2 mg g-1, while the removal percentages were 97.6% and 93.4%, respectively. This approach made it possible to transform volcanic rock powder wastes into an efficient adsorbent to treat contaminated waters with dyes and metals.
Assuntos
Corantes , Poluentes Químicos da Água , Pós , Água , Hidróxido de Sódio , Indicadores e Reagentes , Metais , Adsorção , Cinética , Concentração de Íons de HidrogênioRESUMO
Water pollution by dyes has been a major environmental problem to be tackled, and magnetic adsorbents appear as promising alternatives to solve it. Herein, magnetic activated carbons were prepared by the single-step method from Sapelli wood sawdust, properly characterized, and applied as adsorbents for brilliant blue dye removal. In particular, two magnetic activated carbons, MAC1105 and MAC111, were prepared using the proportion of biomass KOH of 1:1 and varying the proportion of NiCl2 of 0.5 and 1. The characterization results demonstrated that the different proportions of NiCl2 mainly influenced the textural characteristics of the adsorbents. An increase in the surface area from 260.0 to 331.5 m2 g-1 and in the total pore volume from 0.075 to 0.095 cm3 g-1 was observed with the weight ratio of NiCl2. Both adsorbents exhibit ferromagnetic properties and the presence of nanostructured Ni particles. The different properties of the materials influenced the adsorption kinetics and equilibrium of brilliant blue dye. MAC111 showed faster kinetics, reaching the equilibrium in around 10 min, while for MAC1105, it took 60 min for the equilibrium to be reached. In addition, based on the Sips isotherm, the maximum adsorption capacity was 98.12 mg g-1 for MAC111, while for MAC1105, it was 60.73 mg g-1. Furthermore, MAC111 presented the potential to be reused in more adsorption cycles than MAC1105, and the use of the adsorbents in the treatment of a simulated effluent exhibited high effectiveness, with removal efficiencies of up to 90%.
Assuntos
Carvão Vegetal , Poluentes Químicos da Água , Adsorção , Corantes , Fenômenos Magnéticos , Cinética , Azul de Metileno , Concentração de Íons de HidrogênioRESUMO
Adsorption is a promising technology for removing several contaminants from aqueous matrices. In the last years, researchers worldwide have been working on developing composite adsorbents to overcome some limitations and drawbacks of conventional adsorbent materials, which depend on various factors, including the characteristics of the adsorbents. Therefore, it is essential to characterize the composite adsorbents to describe their properties and structure and elucidate the mechanisms, behavior, and phenomenons during the adsorption process. In this sense, this work aimed to review the main methods used for composite adsorbent characterization, providing valuable information on the importance of these techniques in developing new adsorbents. In this paper, we reviewed the following methods: X-Ray diffraction (XRD); spectroscopy; scanning electron microscopy (SEM); N2 adsorption/desorption isotherms (BET and BJH methods); thermogravimetry (TGA); point of zero charge (pHPZC); elemental analysis; proximate analysis; swelling and water retention capacities; desorption and reuse.