Estudo da remoção de corantes em fase líquida utilizando polímeros de coordenação como materiais adsorventes

Abstract

The present study, the synthesis of coordination polymers was realized using the ligand 4,4’- oxybis(benzoic acid) (H2OBA), and two metal-organic frameworks (MOFs), namely MOF808 (Zr) synthesized from the ligand trimesic acid and the metal salt zirconium(IV) chloride, and MIL-101 (Cr)synthesized from the ligand terephthalic acid and the metal salt chromium (III) nitrate. Both MOFs were chemically characterized using powder X-ray diffraction (PXRD), infrared vibrational spectroscopy (IR), elemental analysis for carbon, hydrogen, and nitrogen (CHN), thermal analysis (TG), and nitrogen adsorption analysis (BET). The properly characterized MOFs were employed as adsorbent materials for the adsorption study of two dyes: Sunset Yellow (SY) and Crystal Violet (CV). To optimize the adsorption process of the two dyes using the synthesized MOFs, three variables or factors, namely pH, temperature, and adsorbent mass, were considered in the fractional factorial design of the 3³ Box Behnken Design (BBD). The optimized adsorption conditions for SY were pH 6, MOF-808 (Zr) mass of 18 mg, and temperature of 25 °C, while for MOF-MIL-101 (Cr), the conditions were pH 6.5, MOF mass of 10 mg, and temperature of 25 °C. For Crystal Violet, the optimized conditions were pH 7, MOF mass of 35 mg, and temperature of 45 °C for both MOFs. After the optimization process, a kinetic study was realized for SY combined with the characterized MOFs to evaluate the adsorption kinetic model. The results indicated that chemisorption is the rate-limiting step in the adsorption process for SY. Additionally, a qualitative study was carried out to assess the MOFs' selectivity. When combining solutions of SY and CV, it was observed that the MOFs exhibited a preference for adsorbing SY. Finally, a test was conducted using a sample of wastewater from a textile industry located in the Zona da Mata Mineira to assess the potential of MOFs as adsorbent materials for dyes in a real aqueous matrix. The analysis of the results confirmed the occurrence of adsorption of dyes from the untreated wastewater sample, suggesting that these MOFs are promising candidates as adsorbents for dyes.