Using Straws To Prepare Porous Carbon Electrodes For Electrochemical Adsorption Of Salt Ions In Water

As a necessity of human life,fresh water resources have become one of the most difficult problems in the world.The development and utilization of unconventional water resources and the desalination of saline wastewater are fundamental to solving the shortage of fresh water resources.The common biological method is difficult to treat saline wastewater,so an efficient and energy-saving desalination method is needed.Capacitive deionization technology?CDI?has the advantages of low energy consumption,high efficiency and cleanliness.In practical applications,it is very necessary to find excellent electrode materials with high electro-absorption capacity.In this paper,reed straws are used as raw materials to prepare reed straw-based porous carbon?RSPC?material by pyrolysis and KOH activation treatment.RSPC material has excellent conductivity,good hydrophilicity,and is rich in oxygen-containing functional groups.The electrochemical adsorption property of the material was increased.The amount of activator added and the activation temperature are the main factors affecting the electrical adsorption performance of the material.When the ratio of carbon to KOH is 1:3,and the activation temperature is 800?,the prepared material has the best adsorption effect.Taking the prepared RSPC material as the electrode material of CDI,the influencing factors of capacitance desalting process were analyzed,and the optimum process parameters were obtained:operating voltage 2 V,electrode spacing 3 mm,solution flow rate 15 m L min^-1.The electrode has a salt adsorption capacity of 12.88mg g^-1in a sodium chloride solution with an initial conductivity of 1450?s cm^-1.The adsorption of the electrode in different electrolytes was analyzed,and the valence state and hydration radius of the ions have an effect on the adsorption.After CDI carried out multiple adsorption-desorption cycle experiments,the desalination retention rate was 92.9%.On this basis,a membrane capacitance deionization?MCDI?experiment was carried out.At a voltage of 2 V,the desalination rate of MCDI increased by 58%compared to CDI.And the RSPC electrode has good recycling performance,and the desalination efficiency of 20 cycles reaches 91.88%.