Study On The Optimum Preparation Process Conditions Of Iron Oxide Coated Sand

The Iron Oxide Coated Sands (IOCS) are prepared with ordinary quartz sands and the modifier-FeCl3. To evaluate the static adsorption rate, the surface loading and adherent strength on IOCS, by using the orthogonal test and continuity test, the optimum preparation conditions of IOCS are investigated:Stirring had better not be taken when drying IOCS at 110℃before calcinations, calcining conditions should be controlled:t≥3 h and T≈300℃, the optimal dosing ratio of FeCl3 (2mol/L) to Raw Quartz Sand (RQS) is 0.33 mL FeCl3/g RQS and the optimal dosing ratio of NaOH (3mol/L) to RQS is 0.3 mL NaOH/g RQS.As compared with IOCS-0 prepared by the alkaline deposition method at low temperature (T≤110℃), IOCS-1 which is prepared by calcining IOCS-0 at high temperature (T≈300℃), whose surface loading will be increased by 3～5 times, and desorption rate will decrease by more than 90%.Instead of ordinary modifier-FeCl3, using nanomaterials (such as nano-SiO2, nano-Fe2O3) or activated carbon with high porosity to preparation nano coated sands. The results are shown as follows:The ultrasonic dispersing modifier-SiO2 and preparation at high temperature, can conduce to the nano-SiO2 coating on sands;Nano Iron Oxide Coated Sands (nano-IOCS) appropriate to water bath heating under the condition of continuous stirring, the preparation method that first dosing solvent-HCl, and then dosing precipitat-NaOH can obtain one kind of nano-IOCS, the removal rate of organic reach up to 35.45%; The Single nano SiO2 Coated Sand (S-nano-SICS) and Single nano Iron Oxide Coated Sands (S-nano-IOCS) (to RQS as the carrier), Double nano SiO2 Coated Sand (D-nano-SICS) (to IOCS as the carrier), after the shock absorption, the UV254 of raw humate water increased rather than decreased, and the removal rate were negative.The results of Scanning Electron Microscope (SEM) photographs and X-ray Energy Dispersive Spectrum (EDS) analysis and detection are shown as follows:The main compositions on the surface of IOCS are FesO4 (magnetite) and a-FeOOH(goethite), the surface of IOCS-0 and IOCS-1 is mainlyα-Fe2O3 (hematite), and the surface of nano- IOCS is FeO3.The content ofα-FeOOH (Goethite) on surface loading of IOCS affects adherent strength strongly.By analyzing the SEM photographs, the BET surface area, and the results of nano-modification test, the results are shown as follows:The particle size ofα-Fe2O3 (Hema-tite) attached on the surface of IOCS-1 can be changed by controlling the calcining temp-erature. Changing calcining temperature T, to be able to obtain the IOCS which can remove pollution particles the same size as the iron oxide on the surface of IOCS (pore diameter is about 5～40μm); To urea as precipitating agent,the obtained N-nano-IOCS (pore diameter is about 30～70μm) has larger pores;Using modifier-nano-Fe2O3, can obtain the nano-IOCS (pore diameter is about 0.2～1μm) with nano-scale pore.On the equipment of small scale test for one new water treatment technology, the dyna mic filtration experiment of the best IOCS prepared on the optimum process conditions is tested in order to explore the filtration property and backwash regeneration of this kind of IOCS. The results of the dynamic filtration experiment are shown as follows:The IOCS filter column and activated carbon+IOCS filter column have higher capacity of removal turbidity than the RQS filter column, the average value of removal turbidity is more than 1-2NTU, and the average value of removal UV254 is more than 0.1～2cm-1. By using gas-water backwash, the interception capacity of the filter columns can back to their original level when the filtration period of the inorganic kaolin raw water finished.The backwash method which combines gas-water backwash with desorption agent-NaOH can regenerate IOCS more effectively, followed by the method which combines water backwash with desorption agent-NaOH.