Application of Poly(acrylamide-co-acrylonitrile) Hydrogel to Remove Soluble Water from Biodiesel and Evaluation in the Control Mechanism of the Mass Transfer Process in an Adsorption Process

Abstract

Fuels are contaminated with gases, solvents, dirt, soot, and sealants. Water is always present in biodiesel and high-water content may impact negatively the performance of fuels, such as damaging injection systems and leading up to corrosion of metal surfaces and the growth of fungi and bacteria. The present work shows an alternative technology to remove water from biodiesel by polymeric material. In this context, this work aims to synthesize hydrogel and to evaluate the influence of contact time on the water removal from biodiesel. Poly(acrylamide-co-acrylonitrile) hydrogel was synthesized by means of free radical polymerization. Batch experiments were conducted using particles of this copolymer and saturated-commercial biodiesel at 200 rpm at 25 and 40 °C. The water content of the samples was measured using Karl Fischer technique.
The control mechanism of the mass transfer process between the water present in the fuel and the hydrogel was studied considering pseudo-first order and pseudo-second order kinetic models. The pseudo-second-order model presented better fit from nonlinear experimental data for poly(AAm-co-AC) hydrogel at 25 and 40 ºC. The latter had higher values of R² (0.9963) and maximum water removal capacity (q_e = 247.7 mg/g). The tests carried out in this research pointed out the ability of the hydrogel to reduce water content from biodiesel and to be applied on an industrial scale.