Investigation On Arsenic And Ferric Recovery From Arsenic Waste Water And Value-added Utilization Of Ferric

Recently, waste water from bio-oxidization gold extraction attracts more attention since its strong acidity, high arsenic and ferric concentration, toxity, corrosiveness, etc. Neutralization precipitation with CaO as a precipitation agent, which is recognized as the main technology to treat the waste water from bio-oxidization gold extraction, has much defects, such as massive unstable products, secondary pollution, high cost, waste of resources, etc.. Therefore, to find a simple, safe and effective treatment for the bio-oxidization waste water from gold extraction, and make full use of the ferric and arsenic elements in the waste water have great significance.In this paper, the waste water from bio-oxidization gold extraction in a gold refinary was investigated and treated by a coprecipitation-selective leaching method in which MgO was adopted as a coprecipitation agent, NaOH and Na2CO3were adopted as leaching agents; iron and arsenic elements could be recycled, and nano iron red powder was prepared.The research results are as follows:(1) In the coprecipitation research, the following factors such as pH value, mixing speed and temperature were inspected. The proper coprecipitation conditions are as follows:pH3.5, mixing speed500rpm, and reaction temperature25℃. Under the proper coprecipitation conditions, both the arsenic and ferric are effectively recovered, and the recovery ratio of arsenic and ferric are99.56%and98.71%, respectively.(2) In the selective-leaching research. pH value, leaching temperature.leaching time, liquid-solid ratio. excess sodium carbonate coefficient and aging time were inspected; The proper selective-leaching conditions for separating arsenic from ferric are as follows:pH13.5. ratio of liquid and solid6.5:1, leaching temperature80℃, Leaching time2h, excess sodium carbonate coefficient1.2, aging time1h.Under the proper selective-leaching conditions, the first and second leaching ratios are79.23%and94.58%, respectively;only0.17%of arsenic remains in the solid state, and the arsenic and ferric are basically separated from each other.(3) Kinetic results of the selective-leaching with NaOH as the leaching agents show that: the reaction obeys different laws in the different reaction time.In the first30min. Reaction activation energy (Ea) and Pre-exponential parameter (A) of the raction are respectively15.70KJ·mol-1and1.60.The kinetic equation is:In40to70min, Reacted activation energy (Ea) and Pre-exponential parameter (A) of the raction are respectively23.98KJ·mol-1and6.22.The kinetic equation is: (4) In the preparation research of nano-iron red, influences of calcination temperature and calcination time on the sepecifications of the iron red, such as color, iron oxide content, average particle size, oil obsorption and transparency were inspected. The proper preparation conditions are calcination temperature900℃, calcination time2h. Under the proper preparation conditions, iron red with bright color and better transparency (87.12%) was prepared. The iron red has the average particle size of70.80nm, and has perfect transparency within the light wave range of380～780nm.The test results suggest that the iron red is in line with the requirements of top qualified products according to GB1863-89.