Iron Oxide Based Magnetic Nanocomposites: Removal of Inorganic and Organic Water Contaminants and Antimicrobial Properties

Abstract

In the current scenario, most of the researcher try to prepared novel and cost-effective nanomaterials for wastewater treatment especially discharge from industrial and domestic water, drinking water and contaminated water. A worldwide growing population is one of the major sources of water pollution. The overall thesis demonstrates an extensive view of the use of nanomaterials in water purification using functionalized iron oxide nanomaterials by adsorption of inorganic and organic contaminants.
In the present work, we have prepared iron oxide nanoparticles (Fe3O4) and iron oxide-based nanomaterials such as Fe3O4-TSPED-Tryptophan, Fe3O4-GG, Fe3O4-APTES-EDTA and GO-Fe3O4-APTES of various morphology using precipitation methods. The synthesized nanomaterials were analyzed using FT-IR, XRD, TEM, FE-SEM, VSM, BET surface area, TGA, Zeta potential, Raman and UV-Vis Spectroscopy techniques and were used as effective adsorbent towards heavy metal ions and organic dyes from aqueous solution.
In the first project, we use amino acid (Tryptophan) functionalized iron oxide nanomaterial and TSPED act as a linking agent in between them. The results revealed that the Fe3O4-TSPED-Tryptophan shows greater affinity towards Congo Red (CR) dye adsorption and antibacterial properties. The adsorption efficacy of the dye is assessed by varying various parameters such as pH, dye concentration, adsorbent dose and time. The adsorption isotherm is found to follow Langmuir isotherm model and the rate of adsorption well fitted to pseudo-second-order kinetics. We further checked the antibacterial activity of the dye against gram-negative (Escherichia coli) and gram-positive (Bacillus subtilis) bacterial strain. FTT nanocomposite responds positively towards antibacterial activity.
In the same direction, the second project, functionalized Guar-gum (GG) on the surface of iron oxide (Fe3O4) nanoparticles were synthesized via conventional co-precipitation method. The efficiency of the nanocomposite was investigated towards the adsorption of different dyes such Congo red (CR), Malachite green (MG), Methylene blue (MeB), Methyl orange (MO), Eriochrome Black T (EBT), Methyl blue (MB) and Rhodamine B (Rhb). Among which CR dye shows adsorption efficiency of 97% using the prepared nanocomposite. The presence of -NH2 in the CR dye is responsible for the efficient adsorption, as it easily forms hydrogen bonding with the surface hydroxyl group of Fe3O4-GG. The optimum condition for dye removal efficiency using Fe3O4-GG has been investigated by varying different factors such as the influence of pH, the initial concentration of dye, adsorbent dose and influence of contact time. Moreover, the adsorption procedure was studied with various adsorption isotherms (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Elovich isotherm). Among all isotherm model, Langmuir isotherm model is best fit for CR adsorption. The CR dye adsorption limit was found to be, qm=60.24 mg/g. The dye adsorption rate follows the pseudo-second-order kinetic model.
For the removal of inorganic contaminants, in the third project advancement of an efficient and cost-effective method for heavy metal removal from contaminated water utilizing Fe3O4-APTES-EDTA nanocomposite, a productive reusable adsorbent, is explained in this study. The novel Fe3O4-APTES-EDTA nanocomposite was prepared by three-step process such as (a) firstly Fe3O4 nanoparticle was prepared by chemical co-precipitation method, (b) secondly, the silane coating on the surface of magnetic Fe3O4 cores using linking agent APTES was done which provide amino group (–NH2) for linking with the EDTA molecule and (c) finally, EDTA molecules functions as inclusion sites and a selective containers for trapping different heavy metal ions. Fe3O4-APTES-EDTAis found to be a good adsorbent for Pb2+, Cd2+, Ni2+, Co2+ and Cu2+ removal with a higher adsorption capacity. The maximum adsorption capacity of Pb2+, Cd2+, Ni2+, Co2+, Cu2+ are found to be 11.31, 13.88, 7.64, 4.86 and 78.67 mg/g, respectively. The adsorption and desorption cycle was studied for five cycles with minimal loss of efficiency.
In the fourth project, amino silane magnetic nanocomposite decorated on graphene oxide (GO-Fe3O4-APTES) was successfully prepared by organic transformation reaction followed by co-precipitation method. GO-Fe3O4-APTES material was highly selective for Chromium (VI) removal from aqueous solution. About 91 % of Chromium (VI) was removed at pH 3, 160 rpm of shaking speed, 0.3 g/L of adsorbent dose and 10 hours of contact time. The adsorption process of Chromium (VI) on GO-Fe3O4-APTES follows Pseudo-second-order kinetic and Langmuir isotherm model because of the high correlation coefficient value (R2=0.99). The maximum adsorption capacity (qm) of GO-Fe3O4-APTES was observed at 60.53 mg/g. The synthesized material was desorbed with 0.5 M NaOH and recycled up to five cycles. After five cycles, the removal efficiency of chromium (VI) possesses high efficacy towards-Fe3O4-APTES. Mechanistically, adsorption of Chromium (VI) follows strong electrostatic attraction between adsorbate and adsorbent. GO-Fe3O4-APTES has potential adsorbent for the adsorption of chromium (VI) in wastewater treatment. Furthermore, the Fe3O4-APTES were tested for antibacterial properties against gram-negative (Escherichia coli) and gram-positive (Bacillus subtilis) bacterial strain. The synthesized material responds positively towards antibacterial activity.