Preparation Of Amino Modified Sepiolite And Its Adsorption Properties For Ni²⁺

Nickel is one of the most widely used and expensive heavy metal elements and has the characteristics of non-biodegradability and easy bio-enrichment.In recent years,with the rapid development of industry,it has been widely used in electroplating,electronics and alloys.The improper handling of nickel-containing waste water will not only cause the waste of nickel metal resources,but also cause harm to the eco logical environment and human health.Although there are effective removal methods in the current nickel-containing wastewater treatment technologies,there are widespread defects in high operating costs.Therefore,finding a simple,economical heavy metal wastewater treatment technology has a higher market application value.The clay mineral sepiolite is a natural,abundant,cost-effective natural adsorption material with a certain cation exchange capacity and a large specific surface area,and has been widely used in the removal of dyes,heavy metals,nitrogen and phosphorus and other pollutants.However,the natural sepiolite has a small channel and a lot of impurities,so that its adsorption capacity is limited.If organic modification can be used to introduce sepiolite into groups that have the ability to coordinate with heavy metals,it will not only effectively solve the pollution problem of nickel-containing wastewater,but also broaden the application of sepiolite.In this paper,based on a review of the treatment status of nickel-containing wastewater and the properties of sepiolite,modification methods and its application in wastewater,the following studies were mainly done:1.Aminofunctionalized sepiolite?APTES-SEP?was prepared by modifying the natural sepiolite?SEP?with 3-aminopropyltriethoxysilane?APTES?.The effect of modifier addition amount,modification temperature,and modification time on its adsorption performance was preliminary investigated by single-factor experiments,and response surface methodology was used to further optimize the preparation conditions.The experimental results show that the optimum preparation conditions of modified sepiolite are:APTES dosage is 2.57 CEC,reaction temperature is 72.87°C,and reaction time is 21.41 h.2.X-ray diffraction,infrared spectroscopy,scanning electron microscopy,specific surface and pore structure were used to characterize the modified sepiolite.The characterization results show that the interlayer spacing d110 of the modified sepiolite increases slightly.At the same time,more hydroxyl groups were introduced,and a new-NH2 group appeared.APTES loading was successful on the surface,and the loading of the amino group was 0.0241 mmol·g^-1.In addition,the pores of the modified sepiolite became smoother and the adsorption sites increased.Although the specific surface area slightly decreased from 43 m²·g^-1 to 39 m²·g^-1,the average pore size increased from 2.020 nm to 2.038 nm.These characterization results indicate that APTES modification improves the adsorption properties of sepiolite.3.Comparing APTES-SEP with SEP in wastewater treatment with an initial Ni²⁺concentration of 40 mg·L-1,when the sorbent dosage is 8 g·L-1,initial p H=6,and adsorption time is 6 h,T=At 30°C±1,the Ni²⁺removal rate increased from 50.05%to99.55%,and the maximum adsorption capacity increased from 6.06 mg·g-1 to 15.27 mg·g-1,and the adsorption capacity was greatly improved.4.The Langmuir model can better fit the Ni²⁺adsorption process of the two materials,indicating that the adsorption of Ni²⁺by SEP and APTES-SEP is monolayer adsorption.The pseudo-second-order kinetic equation can describe the adsorption process of Ni²⁺on SEP and APTES-SEP well,and the chemical adsorption process is the rate-limiting step of the whole adsorption reaction.The Gibbs free energy of adsorption reaction is less than zero,indicating that the adsorption process of Ni²⁺on the two materials is spontaneous,and the spontaneous degree of APTES-SEP is greater than that of SEP,indicating that the modification promotes the adsorption of Ni²⁺by sepiolite.5.XPS analysis of the modified sepiolite before and after adsorption of Ni²⁺shows that the adsorption of APTES-SEP to Ni²⁺has a dominant role in coordination adsorption of-NH2 in addition to pore adsorption,ion exchange,and surface hydroxyl complexation.