No abstract

The detection of emerging contaminants in bodies of water has steadily increased in recent years, becoming a severe problem threatening human and ecosystem health. Developing new materials with adsorption properties to remove these pollutants represents an important step toward a potential solution. In this paper, a polybutylene adipate terephthalate (PBAT) nanofibrous membrane incorporating clinoptilolite zeolite was developed and its excellent performance in removing tetracycline (TC) and methylene blue (MB) from water was demonstrated. The composite membrane was prepared in two steps: firstly, a homogeneous dispersion of clinoptilolite (1 wt% respect to polymer) in a PBAT solution (12.6 wt%) was electrospun; secondly, the electrospun membrane was subjected to an acid treatment that improved its wettability through the protonation of the surface silanol groups of clinoptilolite. The resulting membrane was hydrophilic and showed higher adsorption for TC (800 mg/g) and MB (100 mg/g), using a low dose (90 mg/L) powdered zeolite. The maximum removal capacity was obtained at neutral pH, being the cation exchange reaction the main adsorption mechanism. Pseudo-second-order kinetics and Henry’s law agree well with the proposed chemisorption and the high affinity of TC and MB for the adsorbent. The material can be reused after the removal process without generating additional contamination, although losing some effectivity.

Concentrated sulfuric acid is widely used in industrial processes all around the world. Its handling can generate spills with an enormous risk for the operator and the environment. Usually, alkalis are used to remedy this type of spillage, releasing a large amount of heat during the reaction. Absorbent pads are a solution to this problem. Here we present a new and light nanostructured material with extraordinary sorption capacity for concentrated sulfuric acid (98 wt %). The total acid uptake achieved is greater than 1200 wt %, sorbing 12.6 times its own weight of 98 wt % H 2 SO 4 , in just 5 min. It was obtained by applying a green process to a biodegradable polymer (poly(vinyl alcohol), PVA). First, an aqueous solution of PVA was electrospun to get a nanofibrous mat. Then, the mat was heat-treated by two sequential steps below 200 °C (900 min at 155 °C and 420 min at 195 °C). We show that both thermal steps are necessary to maximize acid sorption and that when one of them is not performed, the obtained sorption capacity is much lower (about 400 wt %, sorbing only 4 times its own weight). This phenomenon is explained in terms of transformations of polymeric structures caused by the proposed heat treatment. The sorption mechanism begins with the chemical addition of sulfuric acid to the polymer's surface unsaturations, followed by an increase in surface energy and additional absorption of acid into the material. This study opens up new possibilities for the development of sorbents from environmentally friendly materials and processes.