Adsorption of caffeine using steel wastes

• Published in: Environmental science and pollution research international 2022-11, Vol.29 (53), p.79977-79994
• Main Authors: Duarte, Iara Jennifer Moura, Lima, Thaís Mayra Israel de Oliveira, França, Antonia Mayza de Morais, Buarque, Hugo Leonardo de Brito, do Nascimento, Ronaldo Ferreira
• Format: Article
• Language: English
• Subjects: Adsorbates; Adsorption; Adsorption (and Catalysis or Photocatalysis) Applied to Environmental Protection; Anthropogenic factors; Aquatic Pollution; Aqueous solutions; Atmospheric Protection/Air Quality Control/Air Pollution; Caffeine; Domestic wastewater; Dust; Earth and Environmental Science; Ecotoxicology; Enthalpy; Environment; Environmental Chemistry; Environmental Health; Environmental science; Experimental data; Ferrosoferric Oxide; Fourier transforms; Hematite; Household wastes; Humans; Hydrogen-Ion Concentration; Infrared spectroscopy; Iron; Isotherms; Kinetics; Magnetite; Metal industry wastes; Pharmaceutical Preparations; Scanning electron microscopy; Slag; Spectroscopy, Fourier Transform Infrared; Steel; Surface water; Thermodynamics; Waste Water Technology; Wastes; Wastewater; Water; Water Management; Water Pollutants, Chemical - analysis; Water Pollution Control; X-ray diffraction
• ISSN: 0944-1344; 1614-7499; 1614-7499
• DOI: 10.1007/s11356-022-19582-4

Caffeine is the most widespread active pharmaceutical compound in the world, generally studied as a tracer of human pollution, since caffeine levels in surface water correlate with the anthropogenic load of domestic wastewater. This work investigated the use of different steel wastes named as SW-I, SW-II, SW-II, SW-IV, SW-V, and SW-VI in the adsorption of caffeine. These materials were pretreated and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and point of zero charge. The samples are mainly composed of iron (hematite and magnetite). The caffeine adsorption test indicated that SW-VI (steel slag dust) is the most efficient and promising (removal around 51.68%) in relation to the other residues, which it was selected for further studies. Equilibrium time was reached within 96 h of contact between the adsorbent and the adsorbate, with removal of 84.00%, 81.09%, and 73.19% for the initial concentrations of 10 mg L −1 , 20 mg L −1 , and 30 mg L −1 of caffeine. The pseudo-first-order, pseudo-second-order, and Elovich models presented a good fit to the experimental data. However, the pseudo-first order model described better the experimental behavior. Adsorption isotherms were performed at three temperatures (298, 308, and 318 K). The maximum adsorption capacity was 17.46 ± 2.27 mg g −1 , and experimental data were better fitted by the Sips isotherm. Values of ΔG° and parameters equilibrium of the models of Langmuir, Sips, and Temkin were calculated from the standard enthalpies and standard entropies estimated. The values of ΔG° were negative for the temperatures studied indicating that the adsorption process is viable and spontaneous. Negative values for ΔH° were also found, indicating that the process of caffeine adsorption by SW-VI is an exothermic process (0 to −40 kJ mol −1 ). Thus, the adsorption of caffeine by SW-VI is a physical process. The SW-VI material showed economic viability and promising for the adsorption of caffeine in aqueous media.