| Heavy metal vanadium pollution has seriously threatened the health of the environment and the development of the biology.The discharge of vanadium containing wastewater,which without standerd treatment,can produce serious influence on water,soil,vegetation and the whole ecosystem.In addition,the production of chromate in China accounts for about 35% of the world's total output.Nowadays,non-calcium calcination is the dominated green technology.However,the concentration of vanadium(in V5+)in the leach solution can reach to as high as 500 mg·L-1.Vanadium as an impurity must be removed in order to prepare chromium salt products with required performance.Therefore,research a kind of high efficiency and convenient method for the vanadium ion separation from solution is an imperative subject.In this paper,?-CrOOH was prepared by hygrogen reduction method.K2CrO4 and hydrogen were used as raw material.Cr?OH?3 was prepared via adding alkali into CrCl3·6H2O solution drop by drop.Their properties of static adsoption and dynamic adsorption for vanadium ion in solution were studied.Several simulation solutions were prepared according to the composition of the actual water.The feasibility of the practical application of these two materials were discussed.The following achievements and progresses were exhibited:1)The best adsorption conditions for V5+ with ?-CrOOH were found out to be:solution pH of 2.0,adsorbent dosage of 60:1?nCr: nV?,appropriate adsorption temperature of 30?.After 10.0 h of adsorption,the concentration of vanadium ion in water can be reduce from 300 mg·L-1 to 0.75 mg·L-1.Langmuir isotherm and pseudo-second-order can be used to interpret the adsorption curve and the correlations were good.And the adsorption process was endothermic and spontaneously.Common ions such as NO3-,SO42-,Cl-,Na+,K+,Mg2+ and Ca2+,do not show an obvious influence on the removal efficiencies of vanadium ions.All the removal efficiencies maintain at more than 97%.In the coexistence of chrome and vanadium simulation solution(Na2Cr2O7·2H2O: 150250g·L-1,V5+: 500 mg·L-1),the concentration of vanadium ions can be reduce to lower than44.7 mg·L-1.?-CrOOH was able to realize good desorbed and the vanadium ions in desorption solution can be enrichment and reuse.2)The as-prepared Cr?OH?3was amorphous,with a specific surface area of 312.70m2·g-1 and a pore volume of 0.48 cm3·g-1.High removal efficiencies of vanadium can always be yielded when the solution pH range from 2.0 9.0.The concentration of vanadium ions can be decreased from 500 mg·L-1to 0.81 mg·L-1after 14.0 h of adsoption.The adsorption process can be described by Langmuir isotherm and pseudo-second-order as well.When the common anions?NO3-,SO42-,Cl-?and cations?Na+,K+,Mg2+,Ca2+?existed in the vanadium solution,the removal efficiencies of vanadium ions were still as high as more than 99.6%.In the coexistence of chrome and vanadium simulation solution(Na2Cr2O7·2H2O: 150 250 g·L-1,V5+: 500 mg·L-1),vanadium ions can be removed completely by Cr?OH?3.The vanadium containing wastewater produced by the vanadium precipitation technology of sodium calcination-water leaching-acid ammonium salt was used as a reference and a simulation solution was prepared.After static adsorption process,the removal efficiency of vanadium ions can be as high as 99.88%.Cr?OH?3 can also realize good desorbed and the vanadium ions can be enrichment and reused.3)Column operations were taken with ?-CrOOH and Cr?OH?3,respectively.Single bed and down-flow were used to investigate the dynamic adsorption performance.The results showed that,slower velocity,high loading height and low concentration vanadium ions solution can improve the dynamic adsorption efficiency slightly.?-CrOOH and Cr?OH?3 as novel mesoporous adsorption materials in the aspect of vanadium removal can show good capability and fine performance.Besides,the operation process is easy.The results of this thesis can provide some reference for the further research in water treatment. |
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