Study On Arsenite Removal By In-situ Formed Fe(?) Coagulation And Gravity Membrane Filtration Process

Arsenic is distributed in our environment and is mainly in the form of arsenate,arsenite,and arsenic sulfide.Among the various ways of human arsenic contamination,arsenic contamination in water is in the first place because most of the arsenic compounds are soluble in water.Long-term intake of arsenic can cause arsenic poisoning and cause various health problems.The arsenic removal methods commonly used in water environments include adsorption,electrocoagulation,ion exchange,phytoremediation,bioremediation,biosorption and biofiltration.The traditional arsenic removal process has certain limitations.The in-situ formed Fe(?)coagulation and gravity membrane filtration process is used to remove As(?),and the advantages and feasibility of this process are explored.In this paper,the removal efficiency and mechanism of arsenic in this process under different operating conditions were investigated systematically,and the behavior of coagulation was analyzed.At the same time,the effects of background components in water on the removal of arsenic from the process were investigated,and the effect of the in-situ formed Fe(?)on membrane fouling was investigated.Finally,the arsenic-containing Songhua River water was treated,and the arsenic removal efficiency of the continuous operation of the in-situ formed Fe(?)coagulation and gravity membrane filtration process under the water distribution environment and the actual water body was explored.The results showed that the arsenic removal effect was better under acidic conditions,and the arsenic removal rate decreased sharply under alkaline conditions,and the optimum pH was 6.The zeta potential is different at different pH and is related to the chargeability of the floc surface.The optimum NaClO/Fe ratio is 1:2;the optimum dosage of Fe is 3 mg/L.Different initial As(?)concentration treatment effects are different.In general,the in-situ formed Fe(?)coagulation and gravity membrane filtration process is better than the oxidative coagulation process alone.The oxidative coagulation process alone increases the particle size of the flocs with the reaction time and is in the micron range.The in-situ formed Fe(?)coagulation and gravity membrane filtration process floc size continues to be nanoscale,and the arsenic removal effect is good.The zeta potential of the two processes is not changed from time to time.Fe(II)can be oxidized in a very short time,As(?)has two oxidation pathways,and the effluent arsenic concentrat ion decreases rapidly with the reaction time and remains up to standard.The floc body XRD spectrum has more peak positions and is in an amorphous state.The FTIR spectrum shows that the in-situ formed Fe(?)and the arsenic oxyanion are complexed in the inner layer.The background composition of the water has different effects on the two processes.Under acidic conditions,calcium ions,silicate ions and phosphate ions have little effect on arsenic removal.Under alkaline conditions,calcium ions help to remove arsenic.Silicate and phosphate ions are not favorable due to adsorption competition and iron salt precipitation.In addition to arsenic,the in-situ formed Fe(?)coagulation and gravity membrane filtration process can effectively retain nano-scale floc particles,which has certain advantages.Low concentrations of sulfate ions have little effect on the arsenic removal efficiency of the two processes.Humic acid has a negative impact on the oxidative coagulation process over the entire pH range.The in-situ formed Fe(?)helps to alleviate membrane fouling and is more effective under acidic conditions.The in-situ formed Fe(?)coagulation and gravity membrane filtration process has a good effect on the treatment of arsenic-containing Songhua River water.The new in-situ formed Fe(?)can effectively alleviate membrane pollution and have a certain removal effect on turbidity and organic matter.Exploring the effect of continuous operation of this process on arsenic removal,it can effectively util ize the in-situ formed Fe(?),save resources,and be convenient and efficient.The in-situ formed Fe(?)coagulation and gravity membrane filtration process has a good removal efficiency for As(?)in water environment.It is a convenient and efficient process suitable for China's development.