Pervaporation Membranes for Seawater Desalination Based on Geo-rGO-TiO2 Nanocomposites. Part 1: Microstructure Properties.

Subaer Subaer,Yulprista Putri,Imam Ramadhan,Agung Setiawan,Hamzah Fansuri,Abdul Haris,Resky Irfanita,Misdayanti Misdayanti

doi:10.3390/membranes11120966

Subaer Subaer, Yulprista Putri + Show 6 more

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https://doi.org/10.3390/membranes11120966

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Abstract

This is the first of two papers about the synthesis and microstructure properties of the Geo–rGO–TiO2 ternary nanocomposite, which was designed to suit the criteria of a pervaporation membrane for seawater desalination. The performance and capability of Geo–rGO–TiO2 as a seawater desalination pervaporation membrane are described in the second paper. A geopolymer made from alkali-activated metakaolin was utilized as a binder for the rGO-TiO2 nanocomposite. A modified Hummer’s method was used to synthesize graphene oxide (GO), and a hydrothermal procedure on GO produced reduced graphene oxide (rGO). The adopted approach yielded high-quality GO and rGO, based on Raman spectra results. The nanolayered structure of GO and rGO is revealed by Transmission Electron Microscopy (TEM) images. The Geo–rGO–TiO2 ternary nanocomposite was created by dispersing rGO nanosheets and TiO2 nanoparticles into geopolymer paste and stirring it for several minutes. The mixture was then cured in a sealed mold at 70 °C for one hour. After being demolded, the materials were kept for 28 days before being characterized. Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD) measurements revealed that the geopolymer matrix efficiently bonded the rGO and TiO2, creating nanocomposites. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) was used to examine the morphology of the outer layer and cross-sections of nanocomposites, and the results displayed that rGO were stacked on the surface as well as in the bulk of the geopolymer and will potentially function as nanochannels with a width of around 0.36 nm, while TiO2 NPs covered the majority of the geopolymer matrix, assisting in anti-biofouling of the membranes. The pores structure of the Geo–rGO–TiO2 were classified as micro–meso pores using the Brunauer–Emmet–Teller (BET) method, indicating that they are appropriate for use as pervaporation membranes. The mechanical strength of the membranes was found to be adequate to withstand high water pressure during the pervaporation process. The addition of rGO and TiO2 NPs was found to improve the hyropobicity of the Geo–rGO–TiO2 nanocomposite, preventing excessive seawater penetration into the membrane during the pervaporation process. The results of this study elucidate that the Geo–rGO–TiO2 nanocomposite has a lot of potential for application as a pervaporation membrane for seawater desalination because all of the initial components are widely available and inexpensive.

Highlights

The need for freshwater for drinking and for other beneficial uses is increasing alarmingly as the world population grows and industrialization in most big cities around the world grows rapidly
The goal of this research is to use inorganic nanocomposites comprised of geopolymer as a binder, reduced graphene oxide, and TiO2 NPs as fillers to solve the aforementioned shortcomings of existing saltwater desalination
A ternary nanocomposite based on geopolymer, reduced graphene oxide (rGO), and TiO2 was successfully synsynthesized as a potential inorganic pervaporation membrane for seawater desalination

Summary

Introduction

The need for freshwater for drinking and for other beneficial uses is increasing alarmingly as the world population grows and industrialization in most big cities around the world grows rapidly. Efforts to supply freshwater or drinkable water require new scientific and technological approaches and reasonable investment costs. Almost 98% of the water in the world is seawater, and desalination is the best opportunity to expand the freshwater supply or relieve its shortage. Desalination is a complex process of removing dissolved salts from seawater to produce freshwater. Seawater desalination all over the world is performed through multi-stage flash evaporation (MFE), multi-effect distillation (MED), and reverse osmosis (RO). These methods require high energy consumption and huge investment costs [2,4]

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