Adsorption Of Pb(Ⅱ) And Crystal Violet Aqueous Pollutants By Mptms Modified Alkali-activated Halloysite

Halloysite nanotubes(HNTs)are widely distributed natural clay minerals that stand out among numerous adsorbent materials due to their unique tubular structure and surface properties.However,the hydrophilic nature of halloysite’s surface groups leads to aggregation,making it difficult to disperse effectively within organism,thereby affecting material performance.Surface modification of halloysite with hydrophobic organic silane offers a promising solution to this issue.In this study,a combination of alkali activation and organic silane modification was employed to prepare alkali-activated and 3-mercaptopropyl-trimethoxysilane(MPTMS)surface-modified halloysite nanomaterials.Various characterization techniques,including X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),thermogravimetric analysis(TG/DTG),and scanning electron microscopy(SEM),were utilized to investigate the morphology,structure,surface functional groups,and loading of silane during the alkali activation and silanization process of halloysite.Subsequently,the optimized modified materials were employed for adsorption treatment of Pb(II)and Crystal Violet aqueous pollutants,and the effects and mechanisms of various factors,such as pH,initial pollutant concentration,adsorption time,ionic strength,coexisting ions,temperature,and reusability,on the adsorption performance were explored.The research results are expected to establish a theoretical and experimental basis for the development and preparation of novel organically modified halloysite materials and their practical applications.The main research findings are as follows:(1)The alkali activation treatment of halloysite with 2 mol/L NaOH revealed that the alkali treatment did not cause any shift for the characteristic diffraction peaks of HNTs,and NaOH did not enter the interlayer domains of HNTs during the activation process.SEM confirmed that the activated samples still maintained the tubular morphology at 6 days.It was found that the dissolution rate of silicon in NaOH solution was faster than that of aluminum,and by dissolving the outer wall,reacting with silica-oxygen tetrahedra and exciting Si-OH,the silicon dissolution enters the steady state after 10 days,while the aluminum dissolution shows a slow increase,the silicon dissolution rate and aluminum dissolution rate were consistent with the pseudo-first-order kinetic model.FTIR and TG analysis showed that alkali activation successfully regulated the hydroxyl group on the surface of halloysite,providing more grafting sites for organosilane modification.(2)The organic modification of HNTs with 3-mercaptopropyltrimethoxysilane(MPTMS)revealed that the structure of HNTs was preserved after organic modification,and MPTMS was not significantly entered into the interlayer of HNTs.FTIR and TG analysis results indicated that MPTMS was successfully grafted onto the surface of HNTs.After 6 days of alkali activation,the halloysite modified sample still maintained the tubular morphology and got the maximum silane loading(3.19mass%).(3)The adsorption process of Pb(Ⅱ)by optimized modified materials is highly dependent on pH.At the optimal pH of 5,the adsorption equilibrium can be reached in 120 minutes,and the maximum adsorption capacity at 328 K is 38.2 mg/g.The adsorption kinetics process conforms to the pseudo second order model and the thermodynamics process is more consistent with the Langmuir model.The adsorption process is mainly dominated by complexation of-SH and Pb(II).The reusability performance of the material is poor due to chemisorption.(4)At the optimal pH of 7,the adsorption equilibrium can be reached in 60 minutes,and the maximum adsorption capacity at 328 K is 63.3 mg/g.The adsorption kinetics process is consistent with the pseudo second order model and the thermodynamics process is more consistent with the Langmuir model,and it showed good anti-interference ability in common coexisting ions.Adsorption depends on the distribution between hydrophobic phases,electrostatic attraction and hydrogen bonding,and the reusability performance of the material is general due to the combined effect of physical and chemical adsorption.