چكيده به لاتين
Unique characteristics of hydrogels made them an appropriate choice to use in various applications in single or composite form. In this research, the effective parameters in the production of graphene oxide (GO)-polyvinyl alcohol (PVA) hydrogel composite with the aim of achieving hydrogel with open pores, having appropriate mechanical characteristics, ability to adsorb water pollutions by freezing-thawing method have been investigated. The freezing-thawing process involves the variable number of cycles of placement of the samples after dissolution, in the freezer and then at room temperature for a specified period of time, which leads to changes in the properties of the hydrogel. In the following, other components such as aloe vera, banana peel and polyethylene glycol were also added to the composite to improve its properties.
In addition to the formulas of swelling, porosity, density and gel fraction; Fourier-Transform infrared (FT-IR) Spectroscopy, Ultraviolet-Visible Spectroscopy (UV-Vis), Atomic Absorption Spectroscopy (AAS) and Scanning Electron Microscopy (SEM) analysis were used for bonding, adsorption and microstructure studies.
By using PVA as a polymer, GO and water as a solvent, PVA/GO optimum composite with maximum swelling ratio of 2735%, porosity of 94%, gel fraction of 83%, density of 0.39 ± 0.01 g/cm3 and the adsorption efficiency of methylene blue 99.6% was prepared. This sample contains 5 wt.% polyvinyl Alcohol, 2 wt.% graphene oxide, freezing time of 6 h, thawing time 4 h and 5 freeze-thawing cycles.
Moreover, the sample containing 5 wt.% polyvinyl Alcohol, 1 wt.% graphene oxide, freezing time of 6 h, thawing time 4 h during and 5 freeze-thawing cycles has the optimum strength of 1.6 ± 0. 1 MPa.
At last, the results of adding aloe vera, banana peel and polyethylene glycol to the composite were showed that by the presence of aloe vera and banana peel, this composite has the ability to absorb heavy metals such as lead with an efficiency of 64% and 52%, respectively.
