*Wastewater Treatment Using Imprinted Polymeric Adsorbents DOI: http://dx.doi.org/10.5772/intechopen.92386*

*Waste in Textile and Leather Sectors*

sensitivity and selectivity.

which were the main structure of textile dyes.

when applied in a sample of textile wastewater.

This polymer showed higher binding capacity for methyl green, compared to the corresponding non-imprinted polymer. Electrochemical sensors using the mag-MIP produced by this method have some advantages that it was offering mechanical stability in solution and providing satisfactory performance of sensor in terms of

The fourth example was different example from the others [7]. In this study, Yu et al. is studied selective, sensitive and reliable magnetic molecularly imprinted material to enrich and separate aromatic amines from azo dyes. The 4,4′-methylenebis(2-chloroaniline) (MOCA) was used as template molecule. The synthesis of magnetic molecularly imprinted polymer was performed on the surfaces of the magnetic silica gel spheres via thermal polymerization as mentioned paper, detailly. The steps can be summarized, Fe3O4@SiO2 was prepared and

washed sequentially with both ethanol and toluene. The second step was the surface of Fe3O4@SiO2 was grafted with vinyl by using VETS and triethylamine. The final product of Fe3O4@SiO2@-CH=CH2 was separated and then dispersed in toluene. The synthesis of magnetic molecularly imprinted nanoparticles was done with EGDMA and 2-VP were used as the cross-linker and functional monomer, respectively. A template molecule of MOCA and 2-VP were dispersed in of toluene. Then, particles Fe3O4@SiO2@-CH=CH2, EDGMA and AIBN mixed with the MOCA+2-VP solution and purged with nitrogen. The thermal polymerization was performed with changing temperature. The non-imprinted particles were synthesized with the same procedures in the absence of MOCA. A solution of methanol and acetic acid (9:1, v/v) was used in a Soxhlet to remove the template molecule. The physical properties of mag-MIPs and NIPs were characterized, and the adsorption isotherms were studied. The adsorption process was described by a pseudo-second order model and the equilibrium data fitted well to a Freundlich equation. The other advantages of these magnetic molecularly imprinted polymers were dye removing from wastewaters effectively, and also discriminating carcinogenic aromatic amines

The fifth example was one of real sample application [21]. Foguel et al. is studied MIPs for the Acid Green 16 (AG16) textile dye and the used this MIP for rebinding, selectivity and application of in wastewater samples. MIP synthesis was performed using AG16 dye (template), 1-vinylimidazole (functional monomer), ethyleneglycol-dimethacrylate (cross-linker), 2,2′-azobis(2-methylpropionitrile) (initiator) and methanol (solvent) by bulk polymer synthesis. The imprinted polymer presented excellent rebinding of 83%, an imprinted factor of 6.91 and great selectivity in comparison with other textile dyes. Additionally, the MIP showed high efficiency in the extraction of this dye in wastewater and have a better performance when compared to commercial SPE cartridges. In this study the selectivity of the MIP for AG16 was evaluated using four dyes, commonly used in the textile industry, with different structures and chromophore groups: Direct Yellow 50 (DY50), Acid Red 1 (AR1), Basic Red 9 (BR9) and Methyl Green (MG). MIP for AG16 is quite selective compared to the dyes DY50, AR1, MG and BR9, since approximately 86% of AG16 was bound to the MIP, while the binding percentage for these other four dyes was between 4% and 11%. The MIP proposed in this work showed great efficiency in the determination of the AG16 dye, since the synthesized MIP presented good rebinding of the analyte to the selective cavities of the MIP, high selectivity compared to other textile dyes and efficiency in the extraction of the compound of interest,

The sixth example was about removal and also adsorption of dye on MIPs [22]. Okutucu et al. is studied a molecularly imprinted polymer (MIP) which textile dye (Direct Red 23) was used as template for decolorization of textile wastewater and also used for leaching of this dye from the wastewater by adsorption of onto

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polymer. Acrylamide was used as a monomer and dimethyl sulfoxide was used as a porogen. The ethylene-glycol-dimethacrylate (cross-link), 2,2′-azobis(2 methylpropionitrile) (initiator) was used while preparing bulk polymer by thermal synthesis. The template was removed by methanol:conc. HCl washings. The selective recognition ability of the MIP was studied by an equilibrium-adsorption batch method. The effective adsorption properties of the polymer were tested in synthetic dye wastewater. The high adsorption rate and the amount of imprinted dye that was removed from the polymer was nearly 65%. Eighty percent of the dye was adsorbed by imprinted polymer in synthetic wastewater. The goal of this study is to prepare dye-imprinted polymer to research the molecular recognition characteristics, so that to get valuable results for contamination of dyes in wastewater. It is also important and valuable to recognize dye molecules and their removal from wastewater for the protection of the environment. The dye-imprinted polymer can also be used as a solid-phase adsorbent for Direct Red 23 dye to detect whether it was present in wastewater. Adsorption of dye molecules onto a sorbent can be an effective, low-cost method of decolorization of textile wastewater. Most of the techniques used for this aim were the high cost of production and the regeneration also makes them uneconomical. Molecular imprinting polymers are a new kind of materials which can be economical and effective adsorbents. The removing effect of MIP was seen at **Figure 1**.

The seventh example was the example of using β-cyclodextrin as a monomer for MIP synthesizing [23]. In this study, Hu et al. were synthesized a magnetic β-cyclodextrin polymer (MNP-CM-CDP) which could be used in aqueous media. Kinetic isotherms and a dye adsorption method provided Langmuir. By using MNP-CM-CDP model pollutants (BPA, MB, BO2, RhB, Cr(III), Pb(II), Zn(II), and Cu(II)) were rapidly and efficiently removed from the aqueous solution. Because of magnetic character, the polymer could be easily separated from the solution under an external magnetic field. The synthesis of the magnetic β-cyclodextrin polymer was done at three steps, with TFTPN used as rigid crosslinker, EPI used as flexible crosslinker, chloroacetic used as carboxymethyl agent, Fe3O4 used as magnetic matrix and deionized water used as solvent. First step was, β-TFTPN was dissolved in EPI and then added dropwise to cyclodextrin in NaOH solution. After magnetic stirring for 3 h at 100°C, the solution was filtered. The precipitate was washed with water and THF, and then dried. The second step was synthesis of the CME-CDP. The T-E-CDP was dispersed into NaOH and chloroacetic acid was added. After magnetic stirring, the solution was cooled and neutralized with hydrochloric acid. The CME-CDP was obtained. Third step was synthesis of the MNP-CM-CDP. The magnetic β-cyclodextrin polymer (MNP-CM-CDP) was synthesized by one-step coprecipitation. Fe solutions and the CME-CDP were mixed,

**Figure 1.** *The removal of Direct Red 23 with MIP [12].*

then NH3·H2O (25%, 5 mL) was added dropwise under nitrogen. The precipitate was washed with deionized water five times and then dried. The adsorption of dyes and metal ions is mainly dependent on the pH and this condition was also studied and optimized. The polymerization was performed by green synthesis route, due to use β-cyclodextrin good adsorption performance, easy regeneration, and simple operation. The results indicated that the MNP-CM-CDP is a promising adsorbent in commerce for purifying dyeing wastewater and can be produced on a large scale in industry.
