Nanofiltration Membrane for Water Purification

One of the demanding challenges of the twenty-first century is to improve the decontamination of the water by sustainable and economically adaptable technologies. Traditional water treatment technologies, though efficient, give rise to several problems and not adaptable that obstructs the development processes. The application of membrane technology in wastewater treatment has been gaining great interest and has shown potential results for the elimination of toxic pollutants. Nanofiltration (NF) in membrane technologies is relatively recent development and is explored due to stringent water quality standards. NF has outplaced reverse osmosis in most of the applications due to high flux rates with better pollutant rejection. This chapter incurs to address the principles and concepts of NF membrane technology for water treatment including fundamental mechanism and fouling in the process. Besides, a general outline was made on the different membrane fouling types and mitigation strategies in NF process and future perspectives.

Rapid industrialization and ever-increasing human activities lead to global environmental changes that affect the availability of naturally potable freshwater resources. Affordable and sustainable supply of adequate, clean, and safe water are major challenging concerns in the twenty-first century. Considerable efforts have been made to address the scarcity of safe water, and nanotechnology has emerged as a budding candidate with rapid development. One of the most economical and widely applied technologies for water purification is membrane separation technology. Pressure-driven membrane processes such as nanofiltration have emerged as a critical component of advanced water reuse methods. Key features such as water permeability and high salt rejection of solutes make nanofiltration membranes economically viable for water purification. Thus, the present chapter explores various methods to fabricate the improved nanofiltration membranes with techniques like interfacial polymerization, nanoparticle incorporation, UV treatment, plasma treatment, and layer-by-layer modification. The characterization of the membranes via techniques like scanning electron microscopy, Fourier transform spectroscopy, thermogravimetric analysis etc. are addressed. In addition, the prospects of nanofiltration membrane research and development are also explained.

Nanofiltration (NF) is a preferred process in water and wastewater purification, water recovery, and reuse due to its ability to retain low molecular weight components. However, there is an important factor limiting nanofiltration applications, which is the formation of fouling caused by various pollutants. Pretreating wastewater before entering into the NF process is the most feasible technique to prevent fouling. The pretreatment is aimed to keep the undesirable compounds in the feed water, decrease the concentration of these compounds in the boundary layer, prevent the gel formation/concentration polarization, and/or provide a long membrane service span. At this point, it is critical to select the most appropriate pretreatment methods or configurations based on the characteristics of the wastewater. Pretreatment technologies for NF can be broadly subdivided into chemical (coagulation/flocculation/sedimentation and advanced oxidation), physical (sand/carbon/cartridge filter), biological (MBR/PAC, biosorption), and membrane-based processes (UF/MF). In this section, the combinations of NF-pretreatment technologies studied in various wastewaters are evaluated in terms of factors such as improvement in flux, process sustainability, the water quality of the effluent, and cost.

Polymer-based nanofiltration (NF) membranes are an important class of membrane technology and have been used for filtration and purification of kinds of liquids such as industrial chemicals, solvents, beverages, liquids, water, wastewater on large scale containing ions and molecules. The permeability of the pristine polymeric NF membrane towards a variety of liquids can be modulated by incorporating different kinds of nanomaterials into it. Graphene oxide (GO) is an important class of carbon-based nanomaterial having various properties to make it a suitable meant for manipulating the intrinsic characteristics of the various polymer membranes for filtration applications. Hydrophobic core and hydrophilic surface functionality of GO structure help to modify the applicability of membrane in a variety of ways practically. This chapter mainly focuses on the introduction to various filtration technologies according to sizes of the membrane. Moreover, a method for functionalization, fabrication, and applications of GO-based composite NF membranes is also discussed. Finally, typical uses of GO-based NF membranes for water and wastewater treatment are also summarized.

The rapid growth of population with industrialization leads to a huge negative effect on the sustainability of the environment. Water scarcity through the pollution of the water body is one of the biggest problems for the survival of human civilization as well as life on the Earth. So, the development of water treatment technology is a great challenge to the scientific community for environmental sustainability in the upcoming days. As an energy-efficient technology, nanofiltration shows high importance for drinking water treatment owing to its reliability, integrity, longer cycle lifetime, and lesser cost. Textile wastewater is one of the main sources of pollutant water with hazardous dyes, inorganic salts with higher chemical stability. In this respect, nanofiltration membranes show high importance owing to their superior rejection rates to dyes and inorganic solids. This book chapter gives a powerful discussion about the role of nanofiltration in textile wastewater treatment, mechanistic pathways, different parameters activity, and limitations of this technique. The discussion also includes a future prospective way to recover the limitation with large-scale industrial application.

Water pollution and depletion have developed into global problems over the years, causing damage to the existence of aquatic and people. Water pollution by dye-containing apparel businesses is now recognized as a common wastewater cause. Such industrially polluted water reaches agriculture and consumes the water immediately, causing irreparable human and ecological damage. Consequently, the most appropriate strategy for protecting waterways is the advancement of various sectors to reuse wastewater. A few ecologically acceptable solutions often employed in practical uses are membrane-based nanotechnology. The membrane-assisted remediation technique shows attractive benefits such as power savings, absence of undesired materials, economical and eco-friendly, uninterrupted filtration, and efficiency. Reverse osmosis, nanofiltration, and ultrafiltration are examples of these techniques. Nowadays, ultrafiltration is increasingly vital due to its efficacy in removing contaminants from wastewater. This chapter introduces water pollutants, mainly dyes, and various membrane filtration technologies. This chapter also covers recent membrane filtration methods, their process, application, and dye removal challenges.

Groundwater has been used worldwide due to its ease of access and high quality. At present, groundwater quality has become a matter of concern because it is affected by multiple contaminants present in high concentrations such as nitrate, arsenic, fluoride, heavy metals, etc. Volatile organic compounds (VOCs) are the most prevalent hazardous chemicals that dissolve in water and vaporize in the air. Most of the VOCs are harmful to human health and the environment, such as trihalomethane, perchloroethylene, methyl tert-butyl ether, etc. Prolonged exposure causes dangerous diseases like damage liver, kidneys, nervous system, and some are carcinogenic. Agricultural runoff, septic tanks, landfill leachates, leaky sewage, industrial spillages, and agrochemicals release are the principal source of VOCs emission in groundwater. Oxidation, membrane, adsorption, air stripping, biological, and many other processes have been used to separate VOC. Despite all, nanofiltration (NF) is the newest and most advanced technology with high removal ratio of VOCs at trace level. This chapter begins by introducing different types of groundwater pollutants and NF. This chapter covers all the factors that affect the removal of VOCs. This chapter will cover the recent technologies and discuss the upcoming perspective, critical issues, applicability, and challenges in the presented evolving field.

Seawater or saline water is desalinated by removing salt. Desalination also explains the process of elimination of inorganic ions from a solution to generate safe and potable water. Within this category of desalination, nanofiltration (NF) plays an important role as a subset of membrane processes. A decent prediction model for NF membrane growth can be used for membrane characterization, process modeling, optimization, membrane design and application. As a result of the integrated modeling work, researchers and developers have been able to study different aspects of the phenomenon of separation, formation, adaptation of desalination processes, to smaller extensions and applications possible in the real world. The future of NF membrane development must revolve around solving existing industrial barriers to its development. Consequently, strong academic-industry collaboration should be emphasized. This chapter begins with introducing the desalination and application of various membrane technologies for desalination. This chapter discusses the latest advances in NF membrane technology combined with the fouling of membranes and seawater desalination.

Because of the globe's expanding community and industrialization, there is a greater need for fresh water supplies worldwide. Coatings serve an important part in wastewater purification operations, with innovative applications, continual technological advancements, or cost savings. The much more popular approach to producing biomaterials is stage reversal. Nevertheless, many industrial films are composed of aquaphobic substances, making these highly sensitive to chemical deposition or adsorption on their interface from within their holes. This condition, known colloquially as clogging, is among the most serious operating risks in surface technology. Membrane technology, multiple surface transformation approaches to reduce fouling and increasing porosity at the film interface, application of nanofiltration (NF) membranes, and future potentials are discussed in this chapter. This chapter also covers the advanced modifications and crosslinking techniques to enhance the porosity and longevity of the films used in pressure-driven isolation.

Water scarcity is one of the significant issues many countries face due to the increased demand for freshwater and exhaustion of water resources. Therefore, developing efficient technologies for water purification is anticipated. Nowadays, nanofiltration (NF) separation processes are gaining importance in water purification and pre-treatment for desalination due to their capability in eliminating hardness, salts, and multivalent ions. In addition, NF can be operated under relatively lower pressure than reverse osmosis (RO), where its membrane pore size lies between ultrafiltration (UF) and RO membrane. Polymeric membranes such as polyamide, cellulose acetate, and polyethersulfone are generally used in NF. Many polymeric membranes offer flexibility in the fabrication process and are relatively inexpensive. However, the application of ceramic membranes in water purification has increased hastily due to their beneficial characteristics such as longer life span, fouling resistance, high stability towards corrosive media, and greater mechanical strength. Hence, this chapter discusses the recent signs of progress in ceramic NF membranes for water purification. Various kinds of composite ceramic NF membranes were elaborated in detail, including ceramic-ceramic, ceramic membranes incorporated with nanoparticles and metal–organic frameworks, and ceramic-polymeric membranes. In addition, the implementation of ceramic NF membranes for various water purification methods such as desalination, heavy metal ion removal, removal of dyes, etc., were discussed.

Nanofiltration (NF) membranes have been attaining research interest since the late 1980s, especially in water purification applications; they are very efficient and can selectively remove undesired ions and other organic substances. Various applications of nanofiltration such as treatment of surface and groundwater, removal of organic contaminants and pathogens from water for its reuse are discussed in this chapter. However, a significant disadvantage of any membrane separation process is the fouling phenomenon, adversely affecting membrane efficiency. The fouling phenomenon is majorly dependent on the properties of the membrane and interactions between the solutes and membranes. The present chapter discusses various fouling phenomena such as gel formation, adsorption, deposition, pore blocking, and cake formation in NF membranes. To better understand the fouling, mechanisms involved and various mathematical models to describe fouling are necessary. Therefore, Hermia's models to describe fouling, such as standard pore blocking, complete pore blocking, intermediate pore blocking, and cake filtration models, are discussed in detail. In addition, many researchers are working on fouling mitigation of nanofiltration membranes to avoid fouling. Consequently, this chapter described the various fouling mitigation methods.

Membrane technology in overcoming the problem of poor water quality. It has also become an interesting topic in the environmental issues in this modern era. Membranes have been applied for wetland water treatment which has high number of NOM (natural organic matter). In particular, wetland aquifer bodies is also facing sea water intrusion during hot season and bring out the water become saline. Then, nanofiltration (NF) is one of membranes technology which compatible to treat NOM content in the water. NF membranes are also employed the energy from the driven force. Here, the performance of the membranes such as permeability and selectivity in treated water is calculated. This chapter was providing an overview of the nanofiltration development applied for treating of wetland water. Operation condition which is influencing of NF performance for wetland water treatment has been described. Moreover, separation mechanism of NF and fouling control also clarified in this summary. The performance of NF as well as the operational barriers of NF membranes are discussed for review and future prospects of NF technology are described and conclusions drawn.

The treatment and supply of drinking water are fundamental challenges globally. Different water purification techniques have some setbacks such as the addition of chemicals, energy cost and incapacitated treatment of large volumes of wastewater. Nanofiltration membrane has offered a wide scope for the removal of pollutants from industrial wastewater. This paper provides a review of the nanofiltration mechanism, some factors affecting the nanofiltration membrane, and a summary of the polymer membrane, metal-oxide-based and carbon-based membrane. These material types of the membranes have been demonstrated for the excellent purification and treatment technologies, following these advantages namely; simple scale-up, energy operational condition, environmentally friendliness, compact design, low energy consumption and high separation efficiency. But one of the issues associated with a membrane is fouling. The modification membrane also destroys the surface structure, leading to its instability after long-term filtration and the formation of nanoparticles agglomeration in the membrane matrix. Therefore, physical modification of membrane surfaces, blending with hydrophilic materials will help to control fouling. More research on modification to enhance its performance (decrease in the roughness of the membrane surface and improvement of membrane hydrophilicity) to control fouling should be considered for a holistic membrane performance for wastewater treatment.