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Bioremediation for Sustainable Environmental Cleanup

a solution of dicyandiamide. With this method, the properties of g-C3N4 can be changed by using

different precursors in different solvents. Li et al. (2004) were able to show that highly crystalline

g-C3N4 thin films could be made at room temperature using cyanuric chloride and an acetonitrile

melamine solution. This was done by a simple electrochemical deposition. The shape and size of

g-C3N4 particles were controlled by a combination of the templating method and electrochemical

deposition. Bai et al. (2010) reported hollow g-C3N4 microspheres were produced using different-

sized silica nanospheres. The spheres have an average diameter of about 1 m and are made up of

nanoparticles that range in size from 5 to 30 nm.

17.3.4 The Solvothermal Process

Solvothermal is a way to make something new by reacting the original mixture with organic or

non-aqueous solvents at a certain temperature and pressure in a closed system (like an autoclave).

This method makes materials that have good crystallinity, a shape that can be controlled and

good dispersity. Chen et al. (2018) and Montigaud et al. (2000) reported that cyanuric chloride

and melamine in triethylamine under 130 MPa and 250°C could be used to make g-C3N4.

Guo et al. (2003) made g-C3N4 nanocrystallites by reacting sodium amide and cyanuric chloride with

benzene. Interestingly, g-C3N4 nanotubes were produced when sodium azide substituted sodium

amide. This is likely because sodium azide might change how crystals grow and line up. Bai et al.

(2003) made g-C3N4 by heating ammonium chloride and carbon tetrachloride at 400°C. g-C3N4 can

also be made by a solvothermal reaction using carbon tetrachloride, melamine or dicyandiamide at

4.5 MPa and 290°C (Li et al. 2007).

17.3.5 Thermal Decomposition

Thermal decomposition is a common way to make a lot of g-C3N4 because it uses many resources,

is easy to carry out and does not cost much. Overall, different ways to make g-C3N4 have

different benefits, so researchers should consider their goals when choosing an excellent way to

make g-C3N4. The thermal decomposition of nitrogen-rich precursors like urea, dicyandiamide,

cyanamide, etc., can also be used to produce g-C3N4 (Lan et al. 2016, Shan et al. 2016).

Overall, g-C3N4 can be created by solvothermal reaction, solid-state reaction, electrochemical

deposition and thermal decomposition. The solid-state reaction is not used very often because it needs

high temperatures and pressures, is expensive and harmful to the environment. Electrochemical

deposition can be used to make g-C3N4 film or spheres at room temperature. These materials could

be used to make sensors and photo electrocatalysts, even though this method might not work for

mass production. g-C3N4 with a unique shape can also be made using the solvothermal reaction,

but the process is more complicated and needs high pressure. The most common way to make

g-C3N4 is through thermal decomposition, which is easy and does not cost much. However, more

heat is needed for the process to work, and a lot of ammonia will be produced. The g-C3N4 made

by the thermal decomposition process usually has a bulky structure that restricts its use. Overall,

different ways to make g-C3N4 have multiple benefits, so researchers must consider their goals

when choosing the best way to do it.

17.4 Modifications to Improve Efficiency

To improve the photocatalytic and other applications of g-C3N4, several morphologies with enhanced

properties have been created by heterojunction building and doping with metals, metal oxides and

nonmetals. The modification strategy of g-C3N4, including the creation of composites are covered

here.