ABSTRACT
The scarcity of pure water is a major issue in today’s world. The quality of food and water, which are the basic needs of humans are still a challenge in this twenty-first century. Human activities and rapid industrialization have released many harmful wastes in the environment along with natural calamities. Among these, heavy metal–contaminated water is life-threatening. The solid waste and effluents from the refinery, mining, power plant, metal processing, fertilizer, etc., are major sources of heavy metal contamination in the environment. These metallic components are nonbiodegradable and have the tendency for bioaccumulation. It can disturb and damage the soil biota and affect nutritional value. Their incorporation in the food chain can prove to be toxic to living organisms—humans, animals, and plants. It can affect photosynthesis, protein synthesis, normal growth, and the yield of the plant. In aquatic life, it stimulates reactive oxygen species, which damage fish and other organisms in water by getting accumulated in organs/tissues. Through this food chain, it will be transferred to 98humans, where it can result in a disorder of liver, lungs, kidney, brain functioning, and even cause cancer.
On the other hand, these heavy metals have various uses as raw materials in the production of explosive, fertilizer, pigment, fuel, etc. It is also essential for the growth and development of humans and animals. Hence, their separation and recovery are necessary. Many methods viz. conventional—precipitation, flotation, adsorption, and ion exchange and advanced—membrane-based methods are used to remove it. Conventional method has issues of chemical consumption and toxic sludge production—its disposal, recovery, and high cost considering treatment of secondary pollutant. Membrane methods have high separation efficiency, less space requirement, linear upscaling, need low energy as direct recovery as possible and is sustainable, economical, and environment friendly—no secondary pollution. The main limitation of the membrane method is its fouling and the tradeoff between selectivity and transport rate. Though various materials are reported for the preparation of membranes viz. cellulose acetate, polycarbonate, polyacrylonitrile, polyetherimide, polytetrafluoroethylene, polyethersulfone, polyethylene, polypropylene, polyvinyl chloride, polyamide, polysulfone and polyvinylidene fluoride, and polyetherketone; the limitations are still persistent. These can be overcome by the use of nanomaterial while forming membrane. These nanomaterials will modify the morphology of membranes, thus enhancing the transport property while modifying the selective properties.
Large research is going on all over the world. Various nanoparticles like silver, gold, zinc oxide, salicylate-alumoxane, and carbon are reported for the purpose. Among these, carbon nanomaterial in different forms are found to be more applicable and highly popular. The heavy metal removal efficiency of carbon nanomaterial embedded membranes is excellent, with more than 90% removal efficiency using single membrane composition. This makes them special compared to conventional systems for the formation of membranes to the removal of each component. Additionally, these nanomaterials are also known to provide extraordinary mechanical, chemical, electrical, and thermal stability to the membrane. Carbon nanomaterial incorporated membranes will exhibit high flux, selectivity, conductivity, and resistant to fouling. Thus, they improve the applicability of membranes at actual process conditions. This makes the carbon nanoparticle embedded membranes highly important for actual industrial or domestic applications for heavy metal removal. The current chapter reviews heavy metal removal using carbon nanomaterials incorporated membranes made up of different materials.
