Over last three decades, the important thrust area among the researches are to provide uncontaminated drinking water and for other domestic uses. New technologies in field of water purification are developing steadily but it almost remains same in actual affected fields. In India, one of the main sources for domestic, industrial, agricultural and other purposes is the ground water. The ground water pollution with hazardous anions like fluoride, arsenate
specifically, and other anions like nitrate, phosphate, sulphate, chromate etc. is a major issue that causes various adverse health effects. Many domestic purification processes are there in application, but not exactly applicable in rural area due to many factors like regular maintenance, cost and non-availability of electricity. So there is a huge research gap between
technology available for water purification and its field application in actual affected area. In this project two specific ions fluoride and anions of arsenic are targeted for its removal from water environment.
This dissertation focuses on the remediation of the above-mentioned anionic pollutants by designing suitable materials. Various techniques were applied for the removal of these anionic contaminants so far. Among them adsorption techniques with suitable adsorbent has been an efficient method.
In this present research work, four different types of materials have been synthesized for adsorption of arsenic and fluoride from contaminated water separately. In the first project, we have prepared Fe-Al
6mixed oxide nanoparticle by precipitation method which was used as an adsorbing material to remove fluoride from synthetic aqueous solution. The results revealed that the Fe- Al mixed oxide nanoparticle results better affinity towards fluoride. The maximum adsorption capacity of the material for fluoride was found to be 103.9 mg g-1 with the optimum condition. (0.08 g of the adsorbent, pH 7 and temperature of 40°C). The experimental data are best fitted with Freundlich adsorption isotherm. The pseudo 2nd order kinetic model described the kinetics of adsorption process. In the same direction, in the second project, Chitosan encapsulated magnetic nanoparticle modified was synthesized via co-precipitation method and applied for de-fluoridation of water by adsorption. Experimental results showed that the prepared material works very well for practical purpose. The magnetic chitosan nano particle acts as a good adsorbent for fluoride ions due to interesting interactions of fluoride with amino functionalized Iron. The pseudo 2nd order kinetics is best fitted to the adsorption with a maximum removal capacity of 33.62 mg g-1 calculated from Langmuir isotherm model. In third project, Lanthanum incorporated Zirconium Phosphate mesoporous material was synthesized for remediation of fluoride by precipitation by followed by hydrothermal treatment. The mesostructured Zr-P compounds showed greater removal efficiency due to higher specific surface area. The maximum adsorption capacity of the material for fluoride was 83.90 mg g-1 with the optimum condition at adsorbent dose of 0.2 g, pH 6 and
temperature of 60°C. The adsorption process was best suited to Langmuir adsorption isotherm model and the pseudo 2nd order kinetic model. In the fourth part of this work, Mg/Fe/carbonate layered double hydroxide was prepared for arsenic decontamination by simple precipitation method followed by heat treatment. Presence of the inter layer anions between two cationic layers, facilitates the ion-exchange mechanism for efficient As(V) removal. The maximum removal of arsenic was 271.00 mg g-1 at the optimum condition of
0.1 g of the adsorbent, pH of 7. The equilibrium data of As(V) were best described by Langmuir adsorption isotherm model and kinetics of adsorption followed the pseudo 2nd order kinetic model. To check the role of flow rate, initial concentration and bed volume on adsorption of fluoride ions using synthetic aqueous solution, fixed bed column study was conducted. The mechanism of adsorption process were studied by using analytical methods
like SEM, EDX, TEM, XRD, FTIR, TGA-DSC and BET surface area before and after
treatment. All the results suggested that the above said materials have a strong and specific affinity towards the anionic contaminants, and can be considered as excellent material for treatment of real contaminated water system
