A Study On The Passivation Ability Of Different Passivators For Cu And The Effects On Available Nutrient Elements

With the increasing of heavy metal contamination of soil, the pollution of heavy metal in the soil has become a hot spot in current research. The immobilization is an effective remediation technique of contaminated soils by heavy metals and the choice of passivant is the key of the technology. Nano- black carbon has large surface area, adsorption capacity, is a promising soil conditioner. Na-bentonite modified by pig manure degradation liquid made by natural materials is friendly to the environment and it is also a promising soil conditioner.Based on existing research, three soils Cinnamon soil, Aquic soil, and Acid brown soil were researched. Nano- black carbon oxidized by nitric acid, nano- black carbon oxidized by sulfuric acid, nano-black carbon oxidized by acidic potassium permanganate, Na-bentonite modified by pig manure degradation liquid and Na-bentonite modified by hexadecyl trimethyl ammonium bromide were used as passivators. The adsorption kinetcis and adsorption thermodynamics and effects of nutrients to the adsorption capacity for Cu²⁺ of the passivators were studied. Effects of nutrients to the adsorption ability for Cu²⁺ of nano- black carbon oxidized by nitric acid and Na-bentonite modified by pig manure degradation liquid are studied in the soils, at the same time, effects of the passivators to nutrients were studied.The main results of this paper are as follows:1. The adsorption kinetcis of Cu²⁺ on the five different passivators fit the Langmuir model very well.To nano-black carbon oxidized by nitric acid, nano- black carbon oxidized by sulfuric acid, Na-bentonite modified by hexadecyl trimethyl ammonium bromide and Na-bentonite modified by pig manure degradation liquid, Langmuir model is better than Freundlich model, but as to nano-black carbon oxidized by acidic potassium permanganate, Freundlich model is better than Langmuir model.2. As the concentration of NO₃^- increased, the adsorption ability for Cu²⁺ of Na-bentonite modified by hexadecyl trimethyl ammonium bromide and Na-bentonite modified by pig manure degradation liquid increased at first and then decreased. As to nano- black carbon, it deseased first and then increased; As the concentration of HPO₄^2- increased, the adsorption ability for Cu²⁺ of the five kind of passivators increased; As the concentration of K⁺increased, the adsorption ability for Cu²⁺ of the five kind of passivators increased.Between K⁺and Cu²⁺ there is a clear competitive adsorption.3. Fertilization can make the content of DTPA-Cu increase in the three soils; The available Cu in fertilizer treatments decreased as time went on, controls showed no obvious rule; Treatments applied with passivators available Cu was lower than treatments applied with passivators and fertilizer, indicating that fertilizer applied at the same time with passivators will reduce the effectiveness of passivation;4. In the three soils, the available phosphorus in treatments applied with fertilizer and nano-black carbon oxidized by nitric acid and treatments applied with fertilizer and na-bentonite modified by pig manure degradation liquid is lower than treatments applied with fertilizer, indicating passivators fixed phosphorus in the soils. The available nitrogen in treatments applied with fertilizer and nano-black carbon oxidized by nitric acid is higher than treatments applied with fertilizer because nano-black carbon oxidized by nitric acid take in some NO₃^-. The available potassium in treatments applied with fertilizer and nano-black carbon oxidized by nitric acid is higher than treatments applied with fertilizer because of the desorption of K⁺ from soil colloid.5. The content of available phosphorus, available nitrogen and available potassium will increase if passivators were applied some days after fertilization and 20 days was suggested.