Removal Of Fluoride And Arsenic From Water Using Superconducting Magnetic Adsorption And Separation Technology Based On Iron-based Paramagnetic Material

Nowdays, various technologies, such as reverse osmosis(RO), ion-exchange(IE), coagulation, and adsorptionhave been employed for removing fluoride from water. However, there are restricted by the high operation and maintenance costs, treatment efficiency and complicated operation, there is no good treatment approach for fluoride and arsenic removal.This work proposes a novel process to remove fluoride and arsenic by superconducting magnetic separation with a paramagnetic adsorbentfrom water.In the study of removing fluoride, Fe–Al binary oxidesadsorbents with Fe/Al molar ratios of 1:1, 1:4, and 1:8(Al:Fe, 4Al:Fe and 8Al:Fe) were synthesized by the sol-gel hydrothermal method, the adsorbents were then characterized. The research shows the adsorbents are porous and own amorphous structure. They belong to paramagnetic materials, the magnetization value increase with iron content increased, the pHzpc, specific surface areas and aperture increase with the increase in aluminum.The mean volume particle size of the Al:Fe, 4Al:Fe and 8Al:Fe varies from 72 to 75 μm. Moreover, the adsorption capacity increases with the increase in aluminum.The Langmuir monolayer adsorption capacity of Al:Fe, 4Al:Fe,8Al:Fe for fluoride is35.09mg/g, 45.87 mg/gand56.60mg/g, respectively. The fluoride removal efficiency of 87% can be achieved by FeAlOxHy with superconducting magnetic separation, the fluoride concentration in effluentmeet the WHO drinking water standard. Increasing the magnetic intensities, reducing the flow velocity and diminishing the steel wool size are beneficial to to magnetic separeation. The maximum desorption efficiency of F adsorbed by FeAlOxHy was measured as 92.06% with 0.6 mol/L NaOH.When the adsorbent is determined, the high magnetic intensity, the low flow rate, and the fine steel wool are advantageous in concentrating fluoride in the HGSMS.A maximun fluoride concentration time value of 40 isobtained using FeAlOxHy followed by the HGSMS process. The processing capacity and cost of the 600 mm bore industry-scale superconducting magnetic separator are evaluated The processing capacity and cost of superconducting magnetic separation are 6.9×105m3/a and 2.1yuan/ton,respectively.In the study of removing arsenic, Fe–Mn binary oxides adsorbents with Fe/Mn molar ratios of 3:1, 6:1, and9:1(3Fe:Mn,6Fe:Mn, 9Fe:Mn) are synthesized, the adsorbents were then characterized. The research shows the adsorbents are porous, 6Fe:Mn and 9Fe:Mnare characterized with two-line ferrihydrite structures. The three adsorbents belong to paramagnetic materials, all of the their pHzpcare about 4.0, and their specific surface areas and mean volume particle size vary from 89.2to 283.6 m2/g and25.8 to28.1 μm, respectively.Under the experimental condition of As(III):As(V)=1:1, the removal efficiency of As(III) by 3Fe:Mn, 6Fe:Mn is 13.7%,14.6% higher than the removal efficiency of As(V), respectively, the removal efficiency of As(V) by 9Fe:Mn is 14.1% higher than As(III). Under the experimental condition of As(III):As(V)=1:3, the removal efficiency of As(Total) increases with the increase in Mn. The As(Total) is difficult to be removedunder the condition of As(III):As(V)=3:1. Afer the adsorbents were used for adsorbing arsenic five times, the average arsenic removal efficiency decreased from 86.5% to 38%. The arsenic removal efficiency of 97% can be achieved by FMBO with superconducting magnetic separation, the arsenic concentration in effluentmeet the WHO drinking water standard. Increasing the magnetic intensities, reducing the flow velocity and diminishing the steel wool size are benificial to magnetic separation of Fe–Mn binary oxides. When the adsorbent is determined, the high magnetic intensity, the low flow rate, and the fine steel wool are advantageous in concentrating arsenic in the HGSMS.A maximum arsenic concentration time value of 237 isobtained using Fe–Mn binary oxides followed by the HGSMS process. The processing capacity and cost of the 600 mm bore industry-scale superconducting magnetic separator are evaluated. The processing capacity and cost of superconducting magnetic separation are 4.31×106m3/a and 0.44 yuan/ton, respectively.