| Attapulgite clay(ATP)is a magnesium-rich hydrous aluminosilicate layer chain clay mineral with a special rod-like crystal structure.Due to the ATP chain layer crystal structure,ATP has many unique physical and chemical properties,including water absorption It is widely used in various industries such as chemistry,pharmacy,agriculture and environmental protection.However,the high content of impurities in natural ATP will affect the physical and chemical properties of ATP,thereby reducing its adsorption.In order to improve the adsorption performance of ATP,it needs to be modified before use.The modification methods of ATP are generally divided into inorganic modification,organic modification,acid modification thermal modification,salt modification,ultrasonic modification and so on.Compared with acid modification and organic modification,the residual solution of salt modification is less polluting,easy to handle,relatively cheap and less toxic.Salt modification is mainly based on metal salts such as ferric chloride,ferrous sulfate,aluminum chloride and sodium chloride.After being modified by the metal salt,the metal cation acts to balance the negative charge on the silicon tetrahedron.This kind of low electricity price,the interaction force of the ions with large radius and the structural unit is weak,so the cations between the layers can be exchanged.At the same time,due to the ease of dispersion and peeling under the action of interlayer solvents,ATP has a large specific surface area,and the number of active sites increases,thereby improving its adsorption performance.This research mainly focuses on salt modification..The purpose of this article is to improve the adsorption capacity of ATP through salt modification.Five salt-modified composite adsorbents with different ratios were prepared by salt modification under different conditions.Scanning electron microscope(SEM),Fourier infrared spectroscopy(FT-IR)and powder diffraction(XRD)were used to characterize the salt-modified composite adsorbent.SEM observation and ATP structure analysis before and after modification show that compared with unmodified ATP,salt-modified ATP has a clear pore structure and uniformly dispersed rod-like crystals.FT-IR and XRD characterization showed that after cation exchange,the negative charge of ATP surface and the increase of active sites after salt modification increased,and cation exchange played a major role.The research content is as follows.(1)Through a single factor experiment,the adsorption time(h),p H,temperature(℃),adsorbent dosage(g),adsorbate concentration(mg / L)and other factors were studied for salt-modified ATP to adsorb methylene blue(MB),Cu(Ⅱ),Cr(Ⅵ)adsorption performance,the results found that salt-modified ATP adsorption performance of methylene blue(MB),Cu(Ⅱ),Cr(Ⅵ)is better than ATP.(2)According to the single-factor experiment results,an orthogonal experiment for the adsorption of methylene blue(MB),Cu(Ⅱ)and Cr(Ⅵ)by the salt-modified ATP composite adsorbent was designed,and the optimal composite adsorption conditions of the salt-modified ATP for MB The dosage of salt-modified ATP is 0.800 g,the adsorption time is 1.5h,the temperature is 30 ℃,and the p H = 3.At this time,the adsorption rate is 93.52%.The influence of the main factors affecting the experiment is: the dosage of salt-modified ATP(g)> adsorption time> p H> temperature.The optimal compound adsorption conditions of salt-modified ATP for Cu(Ⅱ)are: the dosage of salt-modified ATP is 0.6g,the adsorption time is 3h,the temperature is 30 ℃,p H = 2,and the adsorption rate at this time is 85.57%.The effect size of the main factors affecting the experiment is: temperature> dosage of salt-modified ATP(g)> p H> adsorption time.The optimal compound adsorption conditions of salt-modified ATP for Cr(Ⅵ)are: the dosage of salt-modified ATP is 0.600 g,the adsorption time is 4h,the temperature is 20 ℃,p H = 5,and the adsorption rate at this time is 82.89%.The influence of the main factors affecting the experiment is: the dosage of salt-modified ATP(g)> temperature> adsorption time> p H.(3)The cyclic desorption experiment proves that the salt-modified ATP exhibits good desorption and regeneration performance.After a certain number of adsorption and desorption,there is still a certain adsorption performance.After three desorptions,the adsorption rate can still reach about 50%..(4)The adsorption thermodynamics and kinetics of MB,Cu(Ⅱ),Cr(Ⅵ)modified by salt-modified ATP were studied.The results show that the adsorption thermodynamics is a multimolecular layer adsorption that conforms to the Freundlich isotherm adsorption model.The adsorption kinetic model is consistent with the quasi-second-order kinetic model,indicating that the adsorption process is chemical adsorption. |
