• Vol 11, No 3 (2020)
  • Chemical Engineering

Effects of Fly Ash Loading on the Characteristics of PVC-based Cation Exchange Membranes for Reverse Electrodialysis

Heru Susanto, Yunita Fahmi, Anisa Tri Hutami, Yuliyanto Triyono Hadi

Corresponding email: heru.susanto@che.undip.ac.id

Cite this article as:
Susanto, H., Fahmi, Y., Hutami, A.T., Hadi, Y.T., 2020. Effects of Fly Ash Loading on the Characteristics of PVC-based Cation Exchange Membranes for Reverse Electrodialysis. International Journal of Technology. Volume 11(3), pp. 544-553

Heru Susanto 1. Department of Chemical Engineering, Faculty of Engineering, Diponegoro University, Jl. Prof. Soedarto, Tembalang, Semarang 50275, Indonesia 2. Membrane Research Center, Integrated Laboratory for R
Yunita Fahmi 1. Department of Chemical Engineering, Faculty of Engineering, Diponegoro University, Jl. Prof. Soedarto, Tembalang, Semarang 50275, Indonesia 2. Membrane Research Center, Integrated Laboratory for R
Anisa Tri Hutami Membrane Research Center, Integrated Laboratory for Research and Services, Diponegoro University, Jl. Prof. Soedarto, Tembalang Semarang 50275, Indonesia
Yuliyanto Triyono Hadi Membrane Research Center, Integrated Laboratory for Research and Services, Diponegoro University, Jl. Prof. Soedarto, Tembalang Semarang 50275, Indonesia
Email to Corresponding Author


This study investigated the effects of fly ash loading on the characteristics of polyvinyl chloride (PVC) membranes for reverse electrodialysis (RED). The membranes were prepared by adding different concentrations of fly ash (0.5–2 wt%) to the casting solution. The surface chemistry of the prepared membranes was analyzed using Fourier transform infrared spectroscopy. The swelling degree (SD) was used as an indicator of the membranes’ water uptake. Titration using NaOH (0.01 M) was performed to measure the membranes’ ion exchange capacity (IEC) and conductivity. The PVC membrane with 2 wt% fly ash demonstrated the highest SD (83.78%), IEC (0.163 meq/g), and conductivity (8.7×10?2 µS/cm). The results show that the presence of fly ash significantly affects the characteristics of PVC membranes for RED.

Cation exchange membrane; Fly ash; Reverse electrodialysis


Global energy scarcity has encouraged efforts to create renewable and sustainable energy (Setiawan et al., 2016). The use of such energy has also become crucial for the prevention of environmental problems. Recently, membrane-based gradient salinity has attracted considerable interest as a prospective renewable and sustainable energy source (Logan and Elimelech, 2015; NRC, 2015). Salinity gradient power can be defined as energy resulting from the mixture of two fluids with different salt concentrations, such as river water and seawater (Hong et al., 2015). The process of power generated through controlled mixing of fresh and salt water has not been explored as extensively as solar and wind power generation or other sustainable power generation methods (Gilstrap, 2013).

There are two methods for salinity difference–based energy generation, namely pressure-retarded osmosis and reverse electrodialysis (RED). In the past few years, researchers have focused on investigating RED for the desalination of river water and seawater (Post and Veerman, 2007). In 1954, Pattle established RED principles, proving that energy can be produced by mixing river water and seawater. Over the last decade, many studies on RED for energy generation were reported (Avci et al., 2018; Mei and Tang, 2018; Moreno et al., 2018; Ciofalo et al., 2019; Mehdizadeh et al., 2019). Lacey (1980) showed that to optimize energy production, membranes with good selectivity and low resistance are required. Turek and Bandura (2007) reported that thin membranes with large contact   areas can improve energy production efficiency by shortening the ion flow pathways.  Thereafter,  efforts to produce membranes  for RED have been proposed (Guler and Nijmeijer, 2018; Luo et al., 2018).

Improving the characteristics of ion exchange membranes through various modification techniques has received considerable attention. Sulfonation and carboxylation aim to supply negative charges to ion exchange membranes. Sulfonation is the most used method for the modification of membranes used in water filtration, dialysis diffusion, electrodialysis, and water cleavage. It is an electrophilic substitution process generally involving aromatic rings and increases membrane charge density, hydrophilicity, and conductivity. Sulfuric acid and chlorosulfate acid are commonly used as sulfonating agents (Hong et al., 2015).

Polyvinyl chloride (PVC) is a versatile thermoplastic polymer that shows appropriate chemical and biological resistances for water applications (Giwa et al., 2019). Inorganic nanoparticles are frequently incorporated into polymeric membrane matrixes to increase the membranes’ performance, including functionality and thermal, chemical, and mechanical stability (Poerwadi et al., 2020). Developments in ion exchange membranes with the introduction of inorganic nanoparticles using aluminum oxide (Hosseini et al., 2012), titanium oxide (Nemati et al., 2015), and iron oxide (Hong and Chen, 2014) have been reported. However, most studies have used pure inorganic nanoparticles, which are either expensive or must be previously synthesized. Numerous inorganic nanoparticles are also available in nature, although their purity may be relatively low. Incorporating such nanoparticles into polymeric membrane matrixes is an interesting prospect.

Fly ash nanoparticles have attracted considerable interest due to their unique properties, including low density and cost and smooth spherical surfaces. More importantly, because fly ash is a coal combustion residue from thermal power plants, its use can offer environmental benefits. The main components of fly ash are oxides of silica, aluminum, iron, and calcium (Janani et al., 2018). Jin et al. (2012) found that the addition of nano-SiO2 in the skin layer improved thermal stability and hydrophilicity and enhanced the nanofiltration membrane’s permeation properties without rejection rate loss.

To the best of our knowledge, there is no research into the utilization of fly ash for fabricating ion exchange membranes. Therefore, this work aimed to study the effects of fly ash loading on the characteristics of membranes for RED. It was hypothesized that the presence of fly ash would improve the membranes’ ion exchange characteristics. 


The composition of the polymer solution significantly influenced the membranes’ properties. Membranes prepared with 2 wt% fly ash content showed the highest SD, IEC, and conductivity. It can thus be concluded that the addition and content of fly ash to PVC membrane solutions significantly affects the characteristics of PVC membranes for RED.


The authors thank the Ministry of Research, Technology, and Higher Education of the Republic of Indonesia (grant number 101-162/UN7.P4.3/PP/2019) for funding this research.


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