The occuring of heavy metals in the environment is a noteworthy worry because of their toxicity. Numerous industrial procedures produce fluid effluents containing heavy metal contaminants. According to the World Health Organization, the metals of most concern and the most widely recognized heavy metal contaminants are Cd, Cr, Cu, Hg, Pb, and Zn. Specifically, cadmium and cadmium mixes are particularly hazardous and profoundly harmful. Therefore, enhanced and imaginative techniques for wastewater treatment are persistently being created to manage and removal of these components. The convergences of these contaminations must be lessened by the method of treatment to meet authoritative standards.
17 2.4.1. Phytoremediation Technology
Phytoremediation method have been quickly portrayed in numerous writing or articles. The non-specific term "phytoremediation" comprises of the Greek prefix Phyto (plant), joined to the Latin root remedium (to right or evacuate an insidiousness) (A. Erakhrumen, A. Agbontalor, 2007) (U. S. Environmental Protection Agency, 2000). Phytoremediation is characterized as a developing innovation utilizing chose plants to clean up the debased environment from risky contaminant to enhance the earth quality.
Figure 1 delineates the uptake systems of both organics and inorganic contaminants through phytoremediation innovation. For organics, it includes phytostabilization, rhizodegradation, rhizofiltration, phytodegradation, and phytovolatilization. These components identified with the natural contaminant property are not ready to be consumed into the plant tissue. For inorganics, instruments which can be included are phytostabilization, rhizofiltration, phytoaccumulation, and phytovolatilization.
Figure 1: Various processes involved in the phytoremediation of heavy metals (Ruchita Dixit, Wasiullah, Deepti Malaviya, Kuppusamy Pandiyan, Udai B. Singh, Asha Sahu, Renu Shukla, Bhanu P. Singh, Jai P. Rai, Pawan Kumar Sharma, Harshad
Lade, Diby Paul, 2015).
18 Plant roots take up metal contaminants and/or abundance supplements from development substrates through rhizofiltration (=root) process, the adsorption, or, precipitation onto plant roots or assimilation into the foundations of contaminants that are in arrangement encompassing the root zone. This procedure is for metals, overabundance supplements, and radionuclide contaminants in groundwater, surface water, and wastewater medium (Prasad & De Oliveira Freitas, 2003).
2.4.2. Nanomaterials
Along with the development of nanotechnology, using nanomaterials is one of the novel method to remove heavy metal particles in aqueous solutions.
With the particle size is very small between 1 nm to 100 nm, nanomaterials active as Sorbents for removing heavy metal ions in water polluted. Several studies have addressed nanoparticles, mainly metal oxides, as effective and efficient adsorbents in the cleanup of environmental contaminants, mainly because nanoparticles can penetrate into the contamination zone where microparticles cannot (Gao, Majumder, Alemany L, Tharangattu, Miguel, Bhebendra, Pradhan, Pulickel, 2011).
Traditional techniques for expelling heavy metals from water and wastewater incorporate electroplating, vanishing, layer filtration, oxidation, decrease, particle trade and adsorption. Among these strategies, adsorption is the best method. Truly, graphite oxide and other carbon-based nanomaterials have been utilized as adsorbent for ecological filtration and water treatment applications for the expulsion of inorganic and natural toxins.
2.4.3 Overview of Graphene Oxide
2.4.3.1 Graphite oxide structures and properties
GO is not a naturally occurring compound; the history of GO research can be dated back to over one hundred and fifty years ago. When it was first made by chemical treatments of graphite with potassium chlorate (KClO3) and fuming nitric
19 acid (HNO3), British chemist Brodie named it graphitic acid or graphite oxide.
Graphene oxide has existed at least six different structure models: Hofmann, Nakajima-Matsuo, Scholz-Boehm, Ruess, Lerf-Klinowski, Décány (Wei GAO, 2012).
As can be seen from figure 1, the soonest demonstrate by Hofmann and Holst in 1939 comprised of epoxy gatherings spreading over the basal planes of graphite, with C/O meets two. The model was modified by Ruess in 1946 with the introduction of hydroxyl groups into the lattice and also the corrugating of the basal plane.
Figure 2: The six proposed structure models of Graphene oxide (Wei GAO, 2012) In 1957, Clauss and Boehm supplemented this commitment with C=C bonds, ketone and analyze gatherings, and also the carboxylic gatherings around the edges. In 1988, Nakajima and Matsuo proposed a phase II sort model (C2F) n in the graphite fluorinated item, and attempted to make the oxide simple for GO. However the majority of the above models have been supplanted by the two latest models named by Lerf-Klinowski and Décány, respectively.
20 2.4.4. Overview of mesoporous composites and SiO2@C@Graphene composite 2.4.4.1. Mesoporous composites
Mesoporous composites synthesis from waste panel glass of TV, notebook, smartphone, and so on. Figure 3 shown the method to synthesis Mesoporous composites. Its components include: 60% SiO2, 18% Al2O3, 8.5% B2O3, 3.0% CaO, 3.0% MgO and 7.5% SrO. This is a very good adsorbent composition.
Figure 3: Synthesis of mesoporous composites from waste panel glass for selective adsorption of heavy metal ions (Yazawa et al., 1984).
21 PART III. METHODS