Research On Phosphorus Removal/Recovery And Electricity Generation By Iron-Air Cell

Metal-air cell is a novel water treatment technology.The iron-air cell is used to treat phosphorus-containing wastewater,and the ferrous ions generated in situ with cheap and easily available zero-valent iron will react with the phosphate in the wastewater.There is no additional energy and no introduction of impurity ions in this novel technology.The phosphorus recovery product vivianite is with higher economic value,and the external circuit generates electricity.The iron-air cell has the functions of"processing waste water","reducing costs","power output",and"P recovery".This paper focuses on the following work:First,construct a dual-chamber iron-air cell that meets the conditions for the formation of vivianite,evaluate the cell’s power generation and phosphorus removal performance under different influencing factors,and optimize the operating conditions of the iron-air cell;Secondly,run the cell continuously under the optimized conditions,monitor the cell dephosphorization,power generation efficiency and product recovery efficiency,evaluate the stability of cell operation,evaluate the economic cost and income-generating benefits of the cell;finally,choose the industrial phosphate-containing wastewater to verify the decontamination,power generation,and phosphorus recovery performance of iron-air batteries,and to explore the application of iron-air batteries in real wastewater.The main results and conclusions are as follows:1、The anolyte pH at 11 has the highest phosphate removal rate constant and phosphate removal rate(0.21 h^-1and 78%),and the change of anolyte pH has little effect on the cell’s power generation;with external resistance of 1000Ωthe average output voltage peaked at 554.44 m V,and with external resistance of 10Ωthe phosphate removal rate constant and phosphate removal rate maximized(0.16 h^-1and75%);When adding 75 g/L Na Cl to the catholyte,the output power reached maximumly at 26.21 W/m³,and adding 35 g/L Na Cl to the catholyte the phosphate reaction rate constant and phosphate removal rate maximized at 0.46 h^-1and 97%;When the concentration of the anolyte Na Cl is 70 g/L,the maximum output power reached maximumly at 58.08 W/m³.The phosphate reaction rate constant and phosphate removal rate maximized at 0.14 h^-1and 68%without the addition of Na Cl.2、The cell can run continuously and stably for 22 cycles（88 days）,and the phosphorus removal efficiency reached 97%in per cycle.With external resistance of1000Ω,the average output voltage of the cell can reach 404 m V,and the maximum output power can reach 14.48 W/m³;vivianite is the main dephosphorization product,and the content of blue iron on the surface of the iron electrode plate and in the bottom of anode chamber sediment were 66.3%and 30%,respectively.3、The iron-air cell has a high removal efficiency for phosphate,with a removal percentage of 80%;the highest electrode potential of the cell can reach 0.98 V,and the highest output power can reach 132.61 W/m³;the phosphorus recovery product is mostly vivianite.The proportion of vivianite is 60%.In addition,the device also showed good removal efficiency for other pollutants in wastewater.The removal percentages of nitrate nitrogen,ammonia nitrogen,COD,Al,and SS were 100%,65%,33%,100%,and 16%,respectively.