( Hydroxy) Iron Oxide and the removal of arsenic in drinking water
|School||Kunming University of Science and Technology|
|Keywords||Iron oxyhydroxides Microwave Adsorption Arse|
Over the years, arsenic is well known for its toxicity, and arsenic contamination of tap water is becoming a worldwide problem. Excessive amounts of arsenic in drinking water may lead to chronic arsenic poisoning and is considered relevant to carcinogenesis and very harmful to human. Currently many methods using to remove arsenic, arsenic removal by adsorption is A-list approach to against arsenic contamination in drinking water. Iron oxides and oxyhydroxides adsorption is the most widely used method to remove arsenic in water, rather than to ion exchange, membrane separation penetration, biological and electrical release arsenic and other methods, it is more effective and cheaper.(1) A novel preparation method of iron oxyhydroxides was developed in this thesis by conventional precipitation and gel method. Aging in water bath at 60℃after 48 hours, we obtained Fe1.833 (OH) 0.5O2.5 iron oxyhydroxides crystals with crystallinity of up to 97.77%. The room temperature deposited suspension completed phase transition from Fe(OH)3→FeOOH→Fe2O3 during the regular 60℃water bath aging from 24h to 168h.(2) The properties of aging samples prepared by conventional heating and microwave heating were compared. The results show that the microwave heating not only shorten the aging time, but also produce oxyhydroxides materials with smaller and more uniform particles and increased crystallinity. Sample aged by 12h microwave heating has uniform grain size with a crystallinity of 98.73%, (110) plane FWHM of 0.110,and mean grain diameter of 466.346A, which is smaller and more uniform than grains obtained by conventional water bath aging method(mean grain diameter of 580.693A). In 77K nitrogen, adsorption isotherms results showed samples obtained by three different aging methods are between typeⅠandⅡ, mainly micropores and mesopores. Microwave-heating aging obtained much higher specific surface area(375.5m2/g) than conventional heating aging(16.93m2/g), indicating that under our experimental conditions, microwave heating aging samples have better iron oxide absorption performance than conventional heating samples. (3) The samples prepared for the removal of arsenic static experiments to study the removal of arsenic adsorbent sample as a result of the removal of arsenic and influencing factors. The samples prepared by adsorption than As (Ⅴ) after the experiment showed that the remaining arsenic content of less than 0.01mg/L, to the WHO on arsenic in drinking water requirements. Samples had a better arsenic removal capacity after Microwave heating aging process. Using the Langmuir and Freundlich isotherm equations fitted the experimental data and found that the microwave radiation iron oxide sample is more in line with the Langmuir adsorption isotherm equation in As (Ⅴ) static adsorption model. This shows that the microwave aging iron oxide sample close to the single molecule adsorption regarding the static adsorption mode for As (Ⅴ).(4) Aging process of oxyhydroxides crystal materials by microwave radiation shortened the preparation time and conserves a lot of energy.12 hours microwave radiation just consumes total power 0.43KW.Generally, a novel preparation method of Iron oxyhydroxides was developed in thesis, which can realize effective and energy saving process.