| In recent years,the treatment and disposal of high-concentration organic wastewater has become the focus and difficulty of water treatment in China,Adsorption technology is considered to be one of the most promising treatment methods for the treatment of wastewater pollution due to its advantages of simple operation,economical and cheap,and good effluent quality.Zirconium hydroxide is an amphoteric oxide with strong alkalinity.It has applications in many industries in production and life,such as pigments,glass and other chemical industries.It has been found in research that it has great potential for the adsorption of organic matter,but consult existing literature It is found that there is no relevant research on its adsorption and desorption performance and adsorption mechanism.This paper studies the adsorption and desorption properties of zirconium hydroxide to high-concentration organic wastewater,and discusses the effects of initial p H of wastewater,dosage of adsorbent,adsorption temperature and adsorption time on adsorption effect;The absorbed zirconium hydroxide was regenerated by soaking in Na OH solution,and the effects of desorption time,concentration,volume and regeneration times of regeneration on the adsorption effect of regeneration were discussed;The thermodynamics,kinetics studies and physical and chemical characterization analysis of the adsorption process were carried out to explore the adsorption mechanism.The main conclusions are as follows:(1)The key factor in the adsorption process is the initial p H of the wastewater.The optimal p H range is 1-2.When the p H rises,the removal rate of organic matter and the amount of adsorption gradually decrease,but the p H below 1 will cause the adsorbent to react directly with H loss.The removal rate of organic matter increases with the increase of the amount of adsorbent,and eventually tends to be stable.The lower the temperature,the better the removal effect of organic matter,indicating that low temperature is beneficial to the adsorption process.The adsorption of zirconium hydroxide to organic matter is a rapid reaction,which basically reaches equilibrium in about 30 minutes.(2)Soak the sodium hydroxide solution to regenerate the adsorbed zirconium hydroxide.The regeneration rate(desorption amount / adsorption amount)is positively correlated with the desorption time.The optimal desorption time is 45 min.The regeneration rate increases with the increase of the concentration of the regeneration liquid,the optimal concentration is 2mol / L,and the regeneration rate can reach 86.86%.As the amount of regeneration liquid increases,the regeneration rate also increases.The solid-liquid ratio of adsorbent to regeneration liquid is 500 g / L,which is the preferred amount of regeneration liquid.When the number of regeneration gradually increased,the adsorption amount of zirconium hydroxide for organic matter slowly decreased.After the seventh regeneration,the adsorption amount was 23.79 mg / g,which was 86.95% of the initial adsorption amount,indicating that the adsorbent still had a good performance after regeneration.Adsorption effect.(3)The adsorption process of zirconium hydroxide to organic matter can be simulated by Langmuir model,indicating that the adsorption is monolayer adsorption.Gibbs function free energy change ΔG is in the range of-20 ~ 0 k J / mol,indicating that the adsorption process belongs to physical adsorption and can proceed spontaneously;The enthalpy change of the adsorption process ΔH is less than zero,indicating that the adsorption can proceed better under low temperature conditions;The entropy change ΔS is greater than zero,indicating that the adsorption process increases the overall chaos of the system.The kinetics of the adsorption process can be simulated with a quasi-twolevel model,indicating that the main influence on the adsorption process is the concentration of organic matter in the wastewater and the nature of zirconium hydroxide itself.(4)The particle size of zirconium hydroxide is small,with an average value of291.4nm.It is a porous frame structure,mainly connected by cement.The surface contains many irregular folds and small pores,which are in an amorphous form.The average pore size before adsorption,after adsorption and after desorption were 5.54 nm,16.2nm,6.40 nm,and the specific surface area was 449.84 m2 /g,188.53 m2/g,350.08m2/g,After the adsorption,the average pore diameter increases compared with before adsorption,and the specific surface area decreases.After desorption,the average pore diameter decreases after adsorption,and the specific surface area rises,but it has not completely recovered to the level before adsorption.There is no obvious change in morphology of zirconium hydroxide after adsorption and desorption.Zirconium hydroxide has better adsorption effect on organic substances with small molecular weight and good water solubility.It mainly relies on intermolecular van der Waals force and hydrogen bonding with organic substances,and can basically recover morphological characteristics and adsorption capacity after desorption regeneration. |
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