Na-rich birnessite（NRB） was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion（NH＋4） from aqueous solution.In order to demonstrate the adsorption perf...Na-rich birnessite（NRB） was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion（NH＋4） from aqueous solution.In order to demonstrate the adsorption performance of the synthesized material,the effects of contact time,pH,initial ammonium ion concentration,and temperature were investigated.Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model.The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated.The monolayer adsorption capacity of the adsorbent,as obtained from the Langmuir isotherm,was 22.61 mg NH＋4-N/g at283 K.Thermodynamic analyses showed that the adsorption was spontaneous and that it was also a physisorption process.Our data revealed that the higher NH＋4adsorption capacity could be primarily attributed to the water absorption process and electrostatic interaction.Particularly,the high surface hydroxyl-content of NRB enables strong interactions with ammonium ion.The results obtained in this study illustrate that the NRB is expected to be an effective and economically viable adsorbent for ammonium ion removal from aqueous system.展开更多
The flotation behaviors of decyltrimethylammonium (103C), dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC) and cetyltrimethylammonium chloride (CTAC) on kaolinite of different part...The flotation behaviors of decyltrimethylammonium (103C), dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC) and cetyltrimethylammonium chloride (CTAC) on kaolinite of different particle size fraction were studied. The adsorbed amount and adsorption isotherms of collectors on kaolinite were determined for painstaking investigation into the adsorption of quaternary amines at kaolinite-water interface by ultraviolet spectrophotometer methods. The flotation results show that the flotation recovery of kaolinite of different particle fraction increases with an increase in pH when 103C, DTAC, TTAC and CTAC are used as collectors. As the concentration of collectors increases, the flotation recovery increases. Particle size of kaolinite has a strong effect on flotation. The flotation recovery of fine kaolinite decreases with the carbon chain of quaternary ammonium salts collectors increasing, while coarse kaolinite is on the contrary. The adsorbed amount tests and adsorption isotherms show that adsorbed amount increases when the particle size of kaolinite increases or when the carbon chain length of quaternary ammonium salts increases. Within the range of flotation collector concentration, the longer the hydrocarbon chain, the more probable to be absolutely adsorbed by fine kaolinite particles and then the lower the collector concentration in the bulk, which leds to lower flotation recovery.展开更多
A bioadsorbent composed of magnetic silica nanoparticles encapsulated by chitosan microspheres was prepared by the emulsion cross-linking method, and it was then modified with quaternary ammonium groups by reaction wi...A bioadsorbent composed of magnetic silica nanoparticles encapsulated by chitosan microspheres was prepared by the emulsion cross-linking method, and it was then modified with quaternary ammonium groups by reaction with ethylenediamine and glycidyl trimethylammonium chloride. Characterization of the bioadsorbent indicated that it was highly acid resistant and magnetically responsive. The bioadsor- bent was then used to remove Cr（VI） from acidic aqueous solution. The results of batch experiments indicated that the optimal pH value was 2.5, and the adsorbent exhibited low pH dependence. The maximum adsorption capacity was 233.1mg/g at pH 2.5 and 25 ℃, and the equilibrium time was deter- mined to be 40-120 min depending on the initial Cr（VI） concentration. The adsorbent could be effectively regenerated using a mixture of 0.3 mol/L NaOH and 0.3 mol/L NaCI with a desorption efficiency of 95.6%, indicating high reusability. In conclusion, the bioadsorbent shows potential for Cr（VI） removal from acidic展开更多
基金supported by the National Natural Science Foundation of China(No.51278409)the Education Department of Shaanxi Province(No.15JS046)
文摘Na-rich birnessite（NRB） was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion（NH＋4） from aqueous solution.In order to demonstrate the adsorption performance of the synthesized material,the effects of contact time,pH,initial ammonium ion concentration,and temperature were investigated.Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model.The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated.The monolayer adsorption capacity of the adsorbent,as obtained from the Langmuir isotherm,was 22.61 mg NH＋4-N/g at283 K.Thermodynamic analyses showed that the adsorption was spontaneous and that it was also a physisorption process.Our data revealed that the higher NH＋4adsorption capacity could be primarily attributed to the water absorption process and electrostatic interaction.Particularly,the high surface hydroxyl-content of NRB enables strong interactions with ammonium ion.The results obtained in this study illustrate that the NRB is expected to be an effective and economically viable adsorbent for ammonium ion removal from aqueous system.
基金the National Natural Science Foundation of China (No.50974134)the National Basic Research Program of China (No.2005CB623701)
文摘The flotation behaviors of decyltrimethylammonium (103C), dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC) and cetyltrimethylammonium chloride (CTAC) on kaolinite of different particle size fraction were studied. The adsorbed amount and adsorption isotherms of collectors on kaolinite were determined for painstaking investigation into the adsorption of quaternary amines at kaolinite-water interface by ultraviolet spectrophotometer methods. The flotation results show that the flotation recovery of kaolinite of different particle fraction increases with an increase in pH when 103C, DTAC, TTAC and CTAC are used as collectors. As the concentration of collectors increases, the flotation recovery increases. Particle size of kaolinite has a strong effect on flotation. The flotation recovery of fine kaolinite decreases with the carbon chain of quaternary ammonium salts collectors increasing, while coarse kaolinite is on the contrary. The adsorbed amount tests and adsorption isotherms show that adsorbed amount increases when the particle size of kaolinite increases or when the carbon chain length of quaternary ammonium salts increases. Within the range of flotation collector concentration, the longer the hydrocarbon chain, the more probable to be absolutely adsorbed by fine kaolinite particles and then the lower the collector concentration in the bulk, which leds to lower flotation recovery.
基金This work was supported by the National Natural Science Foun- dation of China （No. 21106162）, the National Key Natural Science Foundation of China （No. 21136009）, and the Major Project of the National Natural Science Foundation of China （No. 51090382）, the General Research Project of Liaoning Education Department （L2015045）, and the Youth Foundation of Dalian Polytechnic Uni- versity （67007908）.
文摘A bioadsorbent composed of magnetic silica nanoparticles encapsulated by chitosan microspheres was prepared by the emulsion cross-linking method, and it was then modified with quaternary ammonium groups by reaction with ethylenediamine and glycidyl trimethylammonium chloride. Characterization of the bioadsorbent indicated that it was highly acid resistant and magnetically responsive. The bioadsor- bent was then used to remove Cr（VI） from acidic aqueous solution. The results of batch experiments indicated that the optimal pH value was 2.5, and the adsorbent exhibited low pH dependence. The maximum adsorption capacity was 233.1mg/g at pH 2.5 and 25 ℃, and the equilibrium time was deter- mined to be 40-120 min depending on the initial Cr（VI） concentration. The adsorbent could be effectively regenerated using a mixture of 0.3 mol/L NaOH and 0.3 mol/L NaCI with a desorption efficiency of 95.6%, indicating high reusability. In conclusion, the bioadsorbent shows potential for Cr（VI） removal from acidic
