Neutralization Of Arsenic-Containing Acid-Stabilization Of Stinky Arsenic And Arsenic

Arsenic removal of wastewater containing arsenic is an important topic in non-ferrous metal smelting,and scorodite precipitation is one of methods for disposal of high arsenic wastewater.Based on these research,the arsenic removal was studied as the research object.The research content mainly was divided into two parts:(1)to high arsenic pollution of acid in the limestone as reduce pollution sour degrees of cheap raw material,at the same time guarantee that the gypsum contains a very low arsenic,according with standard of recycling experiment research.(2)the residual solution containing large amounts of arsenic the synthesis methods of stable scorodite with ferric salt,efficient and stable remove the arsenic from the solution and it can meet the national standards of storage treatment for a long time.In the process of disposal of high arsenic solution,arsenic solution mixing ferric salt can form scorodite precipitation gradually.Initial arsenic solution pH value,reaction temperature,reaction time and different ratio of arsenic and iron factors all influence on scorodite crystal forming,and the precipitations from experiments were analyzed by XRD analysis,remaining in the solution,leaching toxicity and Fe content changes were all analyzed by ICP analysis.Conclusions are listed as following:(1)In the first step and the course of the experiment,the limestone is the reagent for neutralization of wastewater and quantity will influence the stability of producing gypsum.Through the experimental study shows that when end pH is above 0.5 extracting arsenic content of gypsum is higher than the national standard.Temperatures can influence gypsum toxicity and result show that:the influence of temperature for the formation of gypsum is only a slight effect.In order to reduce cost use this method,and room temperature was chosen to neutralize the acid.By the way room temperature and end pH of 0.5 is the best condition.(2)In the second step by ferric salt to remove arsenic,it was obvious that improving the initial pH value of arsenic solution can obtain higher removal efficiency of As.When Ph was 2,remaining As content of the filtrate show that it is better than the other values of pH at pH=2.Therefore pH=2 was the best condition.Raising the temperature of the reaction process will be beneficial for scorodite crystal formation and growth.This study concluded that the best choice of temperature is 90 ?.Increasing the reaction time will be beneficial for scorodite crystal formation and growth.In order to improve the arsenic substances,the rate of sedimentation and get good crystallization degree.This study considers that the best choice reaction time was 12h.Slightly too much ferric sulfate can promote reaction process in scorodite crystal formation and growth.This research method is unfavorable to add too much ferric composition,therefore ferric and arsenic mole ratio of 1.5 is one of the better parameter selection.Finally through the experimental under the condition of pH=2,reaction temperature at 90 0C,Fe/As=1.5 and reaction for 12 h,there will be scorodite crystal produced which leaching toxicity is lower than the standard 5 mg/L.