Preparation and characterization of thermo-acid-modified palygorskite- loaded nano zero-valent iron and its adsorption of In(III)
Description
The adsorption data of In ( III ) on palygorskite after pretreatment ; the preparation conditions of thermally acid-modified palygorskite-supported nano zero-valent iron composites ( HA-PAL / nZVI ) were optimized； Characterization of the composites, including XRD, FT-IR, BET, SEM-EDS ; the effect of solution acidity on the adsorption of In ( III ) by HA-PAL / nZVI ; adsorption thermodynamic model and thermodynamic parameters ; adsorption kinetic model ; the effects of ionic strength and coexisting components on the adsorption of In ( III ) by HA-PAL / nZVI ; the desorption effect of eluent type and concentration ; XPS analysis and adsorption mechanism
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1 Experimental method 1.1 Clay materials and reagents The palygorskite materials used in the experiments were originally from Baiyin, Gansu, China. High-purity In2O3 (99.99%) was produced from Sichuan High Purity Material Technology Co., Ltd. and the reagents, including nitric acid, sodium pyrophosphate, potassium borohydride, ferrous sulfate heptahydrate, and anhydrous ethanol, were purchased from Chengdu Cologne Chemical Co. 1.2 Preparation of palygorskite-loaded nano zero-valent iron composites 1.2.1 Purification of palygorskite To 500 mL of ultrapure water, add 2.5 g of dispersant (sodium pyrophosphate), and stir for 30 min at 40 oC. Next, add 50 g of raw palygorskite soil, stir for one hour, and let it settle for 30 min. Centrifuge the upper layer of the suspension, wash the bottom material obtained to neutral and dry at 60 oC, and finally purified palygorskite was finely ground through a 200 mesh sieve, sealed and prepared for use. 1.2.2 Thermal and acid modification of palygorskite The purified witch palygorskite was placed in a muffle furnace and burned at different temperatures (250~800 oC) for 2 h to carry out thermal modification; then, the witch palygorskite with the best adsorption effect on In(Ⅲ) and the purified with palygorskite was selected to react with different concentrations of hydrochloric acid, nitric acid, and phosphoric acid (1.0~10.0 M) for 4 h (solid-liquid ratio of 1:10) at 80 oC, respectively. The acid-modified witch palygorskite was washed to neutrality with ultrapure water, dried and finely ground through a 200-mesh sieve. 1.2.3 Preparation of palygorskite-loaded nano zero-valent iron composites Take a quantitative amount of the best pre-treatment effect of different ways of palygorskite into a three-necked flask, add a quantitative amount of FeSO4-7H2O, 100 mL of ethanol (alcohol-water ratio of 1 : 3), stirring ultrasonic; add 40 mL of a certain concentration of KBH4 solution, nitrogen (30 min) at the same time, mechanical stirring for a certain period after the extraction and filtration, deionized water, anhydrous ethanol washed alternately for three times, take out the filter cake, frozen and sealed in a bag. The filter cake was removed, freeze-dried for 24 h, ground and sealed in a bag. 1.3 Adsorption and desorption of In(III) 1.3.1 Adsorption of In(III) 20 mL of In(Ⅲ) solution with a concentration of 100~1150 mg·g−1 (adjusted pH 3.0) was mixed with the quantitative adsorbent and oscillated at a specific temperature. The atomic absorption spectrometer (AA1900, Zhejiang Fuli Analytical Instrument Co., Ltd.) was used to measure the concentration of In(Ⅲ) in the equilibrium solution. 1.3.2 Desorption of In(III) Following the desorption experiment, 20 mL of eluent (NH4Cl, NaOH, HCl, HNO3, and H2SO4) was added, and the mixture was agitated for two hours at room temperature. The adsorbent was then centrifuged and cleaned with ultrapure water until it became neutral. 1.4 characterization 1EDS;2XRD;3FT-IR;4 BET;5XPS.