Preparation Of Lanthanum Hydroxide Nanodispersion By High Gravity Technology And Its Application Research

At present,the application performance of nanodispersions in the field of nanomaterials research stands out and has attracted extensive attention at home and abroad.Compared with nano-powders,nano-dispersions have the characteristics of convenient application,good performance,good compatibility and good dispersibility.Nano-sized lanthanum hydroxide exhibits excellent performance in the application properties of the adsorbed phosphate in water,and thus is widely used as an adsorbent.However,the lanthanum hydroxide as the adsorbent reported in the literature is mostly micron-sized,and the larger the size,the smaller the specific surface area.Therefore,the application performance of the adsorbed phosphate phosphate in the water needs to be improved;Smaller size powders are easy to reunite,In view of this,We have proposed a method for preparing a nano-sized lanthanum hydroxide aqueous phase dispersion which is compatible with water.Various factors were determined to determine the optimal preparation process,and the effect of size and dispersion on the performance of the adsorbed phosphate was investigated.The following is the content and results of the experiment:1.Transparent aqueous nanodispersions of lanthanum hydroxide was prepared by a reaction precipitation method in a conventional stirred tank(ST).The effects of reaction solvent,lanthanum source species,concentration,temperature and pH value of the reaction end point on the preparation of nanodispersion were investigated.The optimal preparation conditions were as follows:the concentration of the reactant was 0.04 mol/L,the reaction temperature is 20?,the pH of the reaction end point was obtained 8,and the aging time is 1 h.Under the optimal conditions,the aqueous nanodispersion of lanthanum hydroxide prepared by the alcohol phase medium had a Zeta potential of 46 mV,a rod shape,a length of 20?30 nm,aspect ratio of 3?6,and hexagonal crystal structure;lanthanum hydroxide nanodispersion prepared by aqueous medium had the particle length of 150?250 nm the aspect ratio of 12?16,and higher stability.2.Transparent aqueous nanodispersions of lanthanum hydroxide were further prepared by a high-gravity reactive precipitation in a rotating packed bed(RPB).The effects of rotating packed bed rotation speed,feed rate,feed ratio and aging time on particle preparation were investigated.The optimum conditions were obtained:RPB speed of 2500 rpm,outer wall temperature of 16?,the flow rate of 100 mL/min,the feed ratio(La(NO3)3:NaOH)of 1:1,the reaction endpoint pH of 8,and the aging time of 1 h,the aging temperature of 160C.The obtained product has a particle length of 60 to 90 nm and a length to diameter ratio of 5 to 10.Compared with the ST product,the RPB product had better transparency and smaller particle size.3.The obtained aqueous nanodispersions of lanthanum hydroxide were further used for phosphate adsorption application.The effects of particle size and dispersion on adsorption performance were explored.The results showed that with the decreased particle length from 200 nm to 30 nm,the maximum adsorption capacity increased from 120.5 mg/g to 150.3 mg/g,improved by 24.7%.This indicated that the smaller particle sizeled to the better adsorption performance.Furthermore,the maximum adsorption capacity of the dispersion of 30 nm was 20%higher than that of the powder with the particle length.Adsorption kinetics and isothermal adsorption studies showed that experimental data were in a good agreement with the quasi-secondary model and the Langmuir isothermal model.Finally,the phosphate adsorption mechanism was studied by X-ray diffraction analysis(XRD)and Fourier transform infrared spectroscopy(FT-IR).