Carbon Nanotubes based Nanocomposites as Photocatalysts in Water Treatment

The shortage of worldwide clean water and the increasing water demand are now ubiquitous problems around the world. Thus, efficient water treatment is an important research topic, of which phocatalysis is known as simplest and efficient technique utilized in the photocatalytic degradation of all major water pollutants, including heavy metal ion, organic and inorganic pollutants. In this context, the use of one- dimensional carbon nanotubes-based nanocomposites in water treatment have been widely demonstrated to be capable of removing persistent organic compounds due to their unique physical and electronic properties, large surface area, tunable morphology, biocompatible and chemical-environmental-thermal stability. This chapter begins with the discussion of the importance and properties of carbon nanotubes, and then briefs about the types and methods of preparation of carbon nanotubes-based nanocomposites in detail. The next section emphasizes the fundamentals of photocatalysis phenomenon and its proposed mechanism for the photocatalytic degradation of pollutants. The last section highlights the recent development in the carbon-based nanocomposites as photocatalyst in water treatment systems, supported by comprehensive literature account. Finally, the remaining challenges and perspectives for using carbon nanotubes-based nanocomposites are discussed.

Photocatalytic Membranes in Degradation of Organic Molecules

Heterogeneous photocatalysis is a technology widely applied to water purification and wastewater treatment under ultraviolet (UV) or even sunlight irradiation for the removal of a variety of environmental pollutants into harmless species. Application of membrane for immobilization of semiconductors and their suitability in photocatalytic degradation of dyes have recently been developed. Integration of photocatalysis with membrane processes significantly improve the membrane separation performance with reducing membrane fouling and improving permeate quality. This paper reviews recent progress in the photocatalytic membranes for wastewater treatment and water purification with an emphasis on the type of membranes, membrane fabrication, and applications in pollutant removal.

Graphitic Carbon Nitride based Photocatalytic Systems for High Performance Hydrogen Production: A Review

Pectin cerium(IV) iodate (PcCeI) and cerium(IV) iodate (CeI) cation ion exchange materials were synthesized via sol–gel methods. The materials were characterized by using Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis, and scanning electron microscopy. The ion exchange capacity (IEC), thermal stability, distribution coefficient (Kd), and pH titrations were investigated to recognize the cation exchange behavior of the materials. The IEC of pectin-cerium(IV) iodate (PcCeI and cerium(IV) iodate CeI were reported as 1.80 meq/g and 0.92 meq/g, respectively. The higher distribution coefficient values of 250.01 and 219.14 mg/L confirmed the selectivity of pectin-cerium(IV) iodate hybrid ion exchanger for As3+ and Zn2+. The antibacterial activity of synthesized ion exchangers was explored for E. coli bacteria and observed relatively higher for PcCeI as compared to CeI.

Composite Ion Exchangers as New Age Photocatalyst

The innovation of different technologies and emphasis on development of new techniques is indispensable to improve the quality of water globally. Photocatalysis is one of the major techniques explored now a days for the exclusion of water impurities using solar light. Different types of photocatalysts have been employed for the removal of dyes, heavy metals, pesticides from aqueous system. During the last few years, nanocomposite ion exchangers were used as a photocatalyst for the removal of organic pollutants. This chapter includes detailed information about introduction of pollutants into the water system, nanocomposite ion exchangers and photocatalysis removal. Nanocomposite ion exchangers effectively degrade various pollutants present in the marine system. These nanocomposites have also been used in different areas such as fuel cell, sensor, nuclear separation and heavy metal removal etc. Therefore, nanocomposite ion exchangers are a new age photocatalyst with unique and effective properties.

Recent advances in Photocatalytic Nitrogen Fixation

Nitrogen fixation is a standout amongst the most significant concoction responses in the biological system of our planet. Under the regularly pressure of the petroleum product exhaustion emergency and anthropogenic worldwide environmental change with ceaseless CO2 emanation in the 21st century, examine focusing on the union of NH3 under gentle conditions in an economical and condition agreeable way is lively and flourishing. Thusly, the focal point of this survey is the cutting edge designing of effective photocatalysts for dinitrogen (N2) obsession toward NH3 amalgamation. Creating green and feasible techniques for NH3 combination under surrounding conditions, utilizing sustainable power source, is firmly wanted, by both modern and logical scientists. Photosynthesis for ammonia synthesis, which has as of late pulled in noteworthy consideration, straightforwardly creates NH3 from daylight, and N2 and H2O by means of photocatalysis. Photocatalysts containing copious surface oxygen-opportunities and coordinative unsaturated metal locales have been demonstrated to be equipped for actuating N2 reduction under fitting photoexcitation. A few impetus materials are examined which incorporate metal oxides, metals sulfides, carbon-based impetuses, and metal nitrides which are for the most part right now being sought after for their better use of their synergist property towards nitrogen fixation. This chapter portrays the photocatalytic reduction systems of nitrate towards unwanted items (nitrite, ammonium) and the more alluring item (dinitrogen).

Photocatalytic Heavy Metal Detoxification from Water Systems

Heavy metals are one of the greatest elevating threat to mankind and other living organisms and it is released into the environment due to increasing dumpsites, transports, and industrial sectors. The industrial wastewater containing heavy metal ions easily enters into the food chain through the air, water, and soil; it results in bioaccumulation and biomagnifications of metal ions in human beings. It causes severe chronic health disorders affecting the nervous system, circulatory system, digestive system and other sensitive organs of the human body. Many conventional techniques such as adsorption, coagulation, flocculation, electrochemical treatment, and biological treatment are used for the reduction of heavy metal ions in the aqueous system. The photocatalysis method is one of the emerging effective ways for eliminating the toxic metal ions from the aqueous solution. This chapter elaborates the principle, mechanism and various methods utilized in the photocatalytic reduction of heavy metal ions from the wastewater.

Perovskites based Nano Heterojunctions for Photocatalytic Pollutant Removal

The development of new generation photocatalytic materials used for the betterment of human as well as environment. Perovskites and perovskites related nano-hetero-junction shows great interest for photocatalytic organic and inorganic pollutant removal. This chapter discusses its crystalline structures varying from cubic (high symmetry) to triclinic (very low symmetry). Various methods have been utilized for synthesis of perovskites such as sol-gel, hydrothermal, vapor deposition methods, solid-state reaction routs from oxide and high pressure technique. The first technique is used for the synthesis of perovskite is ceramic route in which the mixture of oxide was treated at high temperature and processed later by ceramic powder method. Various photocatalyst such as nitrides, sulphides, phosphides, oxide and mixed oxide are employed for photocatalytic water splitting or hydrogen generation. Future perspectives of perovskite-related photocatalyst are included in this chapter.

Photocatalytic Membranes

A photocatalytic membrane can be characterized as a blend between a photocatalyst and membrane; it is promising for taking care of the issues experienced in detachment and photocatalysis. The photocatalyst can deliver, by retention of bright, infrared, or obvious light, compound changes of response accomplices, continually accompanying them into different compound communications without the event of a perpetual change of its synthetic synthesis. There has been significant advancement in the improvement of photocatalytic membrane through joining of metal-oxide photocatalysts to upgrade the presentation of the membranes. An ideal measure of the photocatalyst ought to be consolidated into the membrane to acknowledge sensible photocatalytic action with insignificant outcomes. New improvements in structure and assembling of photocatalytic membranes have made an incredible commitment to the photocatalytic application. Hybridizing photocatalysis with membrane offers photocatalytic response and products partition in a solitary advance and well control of the product maintenance. This section features a portion of the ongoing advances in photocatalytic membrane - kinds of photocatalysts hybridized with the membrane frameworks, reactor design, and average strategies for the creation of photocatalytic membranes, manufacture and membrane application in cleansing and pollutant expulsion from wastewater.

Structural Modifications of Carbon Nitride for Photocatalytic Applications

The current research on photocatalysis is totally focused on the designing and innovation of various low cost materials. For an efficient photocatalyst, there are some aspects which are to be assessed before practical use, such as optical activity, thermal and chemical stability, easy and availability of raw material, biocompatibility, etc. Fortunately, g-C3N4 offers most of these qualities to behave as a star photocatalyst. g-C3N4 could be easily prepared from low cost precursor materials such as urea, melamine, cyanimide and dicyandiamide by simple thermal treatment. Furthermore, larger surface area and two-dimensional planar conjugation structure of g-C3N4 can provide a large platform for anchoring various substrates. Various researchers have utilized g-C3N4 for varieties of applications such as green energy production, energy storage devices, biomedical application, wastewater treatment via photocatalysis and adsorption, photo sensors, etc. Although there are some disadvantages associated with use of g-C3N4 when utilized for various applications. To overcome such hitches various structural modifications have been applied to g-C3N4. The current chapter summarizes a wide mode of applications of g-C3N4 along with various structural modifications which were recently applied to improve the photocatalytic efficacy.

Photocatalytic and Adsorptional Removal of Heavy Metals from Contaminated Water using Nanohybrids

Water contaminated with heavy metals is a major menace for aquatic life and human health consequently its efficient removal remains a crucial challenge for researcher. The utilization of various photocatalytic nanohybrids to synergistically photo-reduce and adsorb heavy metals is a potent strategy to combat water pollution. This book chapter give an overview of the fundamental principle of photocatalysis and various single, binary, ternary and quaternary nanohybrids employed for simultaneous photoreduction and adsorption of heavy metals with its mechanistic insight. Further, conclusion and future prospective as well as limitation of available nanohybrids were addressed. We hope that this book chapter dispenses some noticeable information to heavy metal ions removal from polluted water.