1.1Introduction
Water is one of the most vital resources on the planet. Currently, fresh and clean water supplies have been falling at an alarming rate. More than one billion people do not have access to fresh water, and more than two billion individuals are living in water shortage areas [1]. Since the world population is rising and environmental pollution is increasing rapidly, water purification has to be made more efficient and cost-effective. Access to clean water has been recognized as a serious challenge for the world’s social and economic growth. The advancement of alternative water supplies is crucial and essential. One of the current challenges is to develop effective and less energy consuming process through treating and recovering of pure water from groundwater, industrial, and brackish water [2]. Removal of heavy metals and other contaminants from water and wastewater is a very important factor with respect to environmental pollution control and human health. Several methods have been used for the removal of heavy metal ions and other contaminants from aqueous solutions, including ion exchange, chemical precipitation, electrodialysis, and solvent extraction. However, these techniques are associated with problems such as excessive time requirements, high costs, and high energy consumption. Moreover, adsorption method can be considered as an effective and widely used process for removal of heavy metals and other contaminants from wastewater due to its simplicity, moderate operational conditions, and economic feasibility. The most important properties of any adsorbent are its surface area and structure [3]. However, particulate or powder adsorbents might re-pollute treated water because of the tremendous problems in recovery.
Among the different water purification technologies, the pressure-driven membrane filtration processes—microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO)—are the most energy efficient processes. Distillation process consumes more energy as compared to the membrane filtration processes, which are relatively fast, efficient, and practical [4]. Depending on the impact of various constituents of water on human health crops and industrial processes, certain water and stream water standards have been laid down by different standard institutions such as Bureau of Indian Standards (BIS), Indian Council of Medical Research (ICMR), World Health Organisation (WHO), and Food and Agriculture Organization (FAO) of United Nations for deciding the suitability of water for drinking and irrigation use. Table 1.1 [5] summarizes the drinking water standards.
Table 1.1List of Inorganic Chemicals and Their Maximum Contaminant Level (MCL) in Drinking Water Contaminant | MCL (mg/L) | Potential Health Effects: Above the Limit | Public Health Goal (mg/L) |
Arsenic | 0.01 | Skin damage or problems with circulatory systems may have increased risk of getting cancer | Zero |
Cadmium | 0.005 | Kidney damage | 0.005 |
Chromium (total) | 0.1 | Allergic dermatitis | 0.1 |
Copper | 1.3 | Liver or kidney damage | 1.3 |
Fluoride | 1.5 | Pain and tenderness of the bones Children may get mottled teeth | 1.0 |
Iron | 0.3 | Leave the water with brown-red color aesthetic problems | <0.3 |
Lead | 0.015 | Infants and children: Delays in physical or mental development. Adults: Kidney problems; high blood pressure | Zero |
Mercury | 0.002 | Kidney damage | 0.002 |
1.2General Background
1.2.1Preparation of Synthetic Membranes
Currently, membranes and membrane separation techniques have grown from a simple laboratory tool to an industrial process with considerable technical and commercial impact. Today, membranes are used on a large scale to produce potable water from the sea by reverse osmosis; to clean industrial effluents and recover valuable constituents by electrodialysis; to fractionate macromolecular solutions in the food and drug industry by ultrafiltration; to remove urea and other toxins from the bloodstream by dialysis in an artificial kidney; and to release drugs at a predetermined rate in medical treatment. Although membrane processes may be different in their mode of operation, in the structures used as separating barriers, and in the driving forces used for the transport of the different chemical components, they have several features in common that make them attractive as a separation tool. In several cases, membrane processes are faster, more efficient, and more economical than conventional separation techniques [6]. During membrane process, the separation is usually performed at ambient temperature, thus allowing temperat...
