RESUMO
The growing consumption of anxiolytic drugs like diazepam (DZP) has aggravated the problem of persistent organic pollutants in water. Due to its characteristics, the removal of DZP from water and wastewater is a challenging task. As an effort to deals with this issue, in this study, we report the development of a hydrogel based on Gum Arabic (GA) grafted with poly(acrylic acid) (GA-g-PAAc) to be used in the adsorptive removal of DZP from water. The hydrogel formation was confirmed by Fourier-transform infrared (FTIR) spectroscopy and thermal analysis (TGA/DTG) analyses. Images obtained by scanning electron microscopy (SEM) revealed that GA-g-PAAc hydrogel exhibits a porous morphology while swelling experiments suggest a superabsorbent characteristic (degree of swelling> 600%). From batch experiments, it was found that the removal of DZP reached remarkable percentages (>80%) before 300 min in moderate experimental conditions (pH 7, 25 °C, 150 mg of adsorbent). The adsorption of DZP on GA-g-PAAc followed the pseudo-first order kinetics, and the mechanism was described by the linear Langmuir isotherm. The maximum adsorption capacity (qmax) was calculated to be 15.16 mg g-1 (at 25 °C), which is comparable or superior to other adsorbent materials used in DZP removal. Reuse experiments showed that GA-g-PAAc keeps appreciable adsorption ability even after five reuse cycles. The results reported here suggest this superabsorbent hydrogel could be a promising adsorbent material to treat water contaminated by anxiolytic drugs, like DZP.
