A Highly Efficient Nanostructured Sorbent of Sulfuric Acid from Ecofriendly Electrospun Poly(vinyl alcohol) Mats

Abstract

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 % H2SO4, 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.