Silicon Nitride Colloidal Probe Measurements: Interparticle Forces and the Role of Surface-Segment Interactions in Poly(acrylic acid) Adsorption from Aqueous Solution

Direct measurements of forces between silicon nitride surfaces in the presence of poly(acrylic acid) (PAA) are presented. The force-distance curves were obtained at pH > pH_iep with an atomic force microscopy (AFM) colloidal-probe technique using a novel spherical silicon nitride probe attached to the AFM cantilever. We found that PAA adsorbs onto the negatively charged silicon nitride surface, which results in an increased repulsive surface potential. The steric contribution to the interparticle repulsion is small and the layer conformation remains flat even at high surface potentials or high ionic strength. The general features of the stabilization of ceramic powders with PAA are discussed; we suggest that PAA adsorbs onto silicon nitride by sequential adsorption of neighboring segments ("zipping"), which results in a flat conformation. In contrast, the long-range steric force found in the ZrO₂/PAA system at pH > pH_iep arises because the stretched equilibrium bulk conformation of the highly charged polymer is preserved via the formation of strong, irreversible surface-segment bonds on adsorption.     

稀土元素对CO络合吸附剂结构及性能的影响

比较了吸附剂微孔结构 ,考察了添加稀土元素对CO络合吸附剂的微孔结构及性能的影响 ,探讨了其促进机理 ,结果表明 ,WHTX粉状活性炭作载体 ,微孔尺寸均一 ,BET比表面积最大 ;而稀土元素可改善CO络合吸附剂的微孔结构 ,明显增大孔容积 ,促进了对CO的吸附性能。吸附与脱附性能试验说明了吸附剂变压再生的可能性 ,这为CO变压吸附过程的节能开发奠定了一定的基础。     

Synthesis of amorphous KAlSi3O8 for cesium radionuclide immobilization into solid matrices using spark plasma sintering technique

An effective sorption material for cesium radionuclides immobilization in highly safe and reliable solid-state matrices was proposed. Prepared aluminosilicate (КAlSi₃O₈) adsorbent had amorphous mesoporous structure and Cs⁺ ions sorption capacity of ～3.7 mmol/g. The physical-chemical characteristics of (Cs, К)AlSi₃O₈ sample saturated with Cs ⁺ ions were studied using XRD, FT-IR, SEM-EDX, and DTA-TG methods. Firstly, solid-state aluminosilicate matrices were obtained using spark plasma sintering (SPS) technology with high values of relative density (up to 99.9%), compressive strength (31.3–79.2 MPa), and Vickers microhardness (0.9–5.3 GPa). The sample obtained at 1000 °C had a low value of Cs⁺ leaching from matrices (R_Cs within the range of 10^-7 g cm^-2·day^-1) and cesium diffusion coefficient (D_e 9.07 × 10^-14 cm²/s). It was shown that prepared aluminosilicate cesium matrices comply with regulatory requirements of GOST R 50926-96 and ANSI/ANS 16.1.     

Purification of water from heavy metal of lead by nanocomposite of Ce-TZP/Al2O3

In this study, nanocomposites of Ce-TZP/Al₂O₃ with four different mole percent of alumina from 20% to 80% were prepared by aqueous combustion synthesis method and effects of alumina mole fraction on the adsorption of lead ions were investigated. Lead (Pb²⁺) ion adsorption process was performed at the temperature of 25°C, contact time of 100 minutes for all the samples. The results showed that as the alumina content increases in the nanocomposite, the adsorption capacity of lead increases which was 63.72% for the nanocomposite containing 80% alumina. X-ray diffractometry and scanning electron microscopy were applied to characterize the powders and the samples after the adsorption reaction.     

以MgO为模板剂制备纳米中孔炭及其应用研究进展

无需任何稳定和活化过程,采用MgO为模板剂,选择不同的碳前驱体可制备高比表面积且含有大量中孔的活性炭.综述了具体制备方法、制备条件对孔结构的影响、纳米孔结构形成机理、该方法的优点以及该法所得纳米中孔活性炭的应用前景.通过选择不同的MgO前驱体可调节活性炭中孔大小;而中孔和微孔的相对体积则由碳前驱体控制.采用该法制备的中孔炭作为电容器、吸附材料等在能源、资源和环境方面的应用前景相当广阔.     

直接空气捕集CO2吸附剂综述

综述直接空气捕集CO₂吸附剂的研究进展,对比碱/碱土金属基吸附剂、金属有机框架吸附剂、负载胺基吸附剂、变湿吸附剂的优缺点,从吸附容量与胺效率、动力学与载体选择、再生方式与能耗、热稳定性与抗降解等方面对吸附剂性能进行评估. 简要叙述相关工程示范项目和技术经济性;总结研究中存在的问题,展望未来的研究方向.     

Photocatalytic Activity of Monodispersed Spherical TiO2 Particles with Different Crystallization Routes

Monodispersed spherical TiO₂ particles were prepared by hydrothermal crystallization and/or calcination of spherical amorphous particles, synthesized by thermal hydrolysis of TiCl₄. The crystallized spherical particles were secondary agglomerates of primary nanocrystallites. Different crystallization routes and conditions provided the spherical TiO₂ particles with wide particle characteristics, such as the fraction of crystallization, the size and shape of the primary nanocrystallites, and the specific surface area. The photocatalytic activity showed complex dependence on the crystallization routes and conditions. The complex dependence behavior could be explained by combining the effects of the fraction of crystallization, the specific surface area, and the adsorption ability for hydroxyl ions. Especially, in the present study, the hydrothermally crystallized TiO₂ particles with large primary nanocrystallites showed the highest photocatalytic activity. The high photocatalytic activity mainly resulted from the high surface adsorption ability for hydroxyl ions, which was closely related to the well-developed (flat and faceted) morphology of primary nanocrystallite.     

Adsorption behavior of uranyl ions onto amino-type adsorbents prepared by radiation-induced graft copolymerization

Amino-type adsorbents(ATAs) were prepared by radiation-induced graft copolymerization of 4-hydroxybutyl acry late glycidyl ether(HB) onto a polyethylene-coated polypropylene(PE/PP) duplex fiber of a non-woven fabric,and modified with different amines of ethylenediamine(EDA),diethylenetriamine(DETA),triethylenetetramine(TETA) and diethylamine(DEA).The adsorption behavior of uranyl ions onto the ATAs was studied in batch experiments.The effects of the contact time,initial concentration of the ions,temperature,and pH value.The salinity were investigated along with the adsorption kinetics and the adsorption isotherms.The kinetic experimental data followed the pseudo second-order kinetic model,and the adsorption isotherms correlated well with the Langmuir model.The ATAs showed good efficiency in adsorbing uranyl ions,with the best saturation adsorption capacity being 64.26 mg g~(-1) for ATA-DETA within 120 min.The temperature dependence of ATADETA was quite abnormal and the quickest behavior was obtained at 25 ℃.ATAs showed good adsorption capacity over a wide pH range of 4.0-8.5,and HCl could be used in the elution process.Salinity of the solution had great effect on the adsorption capacity,3.5%salinity resulted in a 55%loss of capacity from ATA-DETA.The selectivity of ATA-DETA showed an order of:UO_2~(2+)≈Fe~(3+) Zn~(2+) VO_3~- Co~(2+) Ni~(2+).     

Structure Control of Calcium Silicate Hydrate Gels for Dye Removal Applications

The structure of calcium silicate hydrate (C‐S‐H) gels was modified by hydrothermal reaction with aqueous acetic acid solvent, and then the C‐S‐H gels were used for dye removal from aqueous solution. With increasing acetic acid concentration, the Ca:Si molar ratio decreased and the length of the silicate anion chain structure of the C‐S‐H gels increased. The silicate anion chain length affects the number of available silanol groups on the surface of the C‐S‐H gel: the longer the silicate anion chain length, the greater the number of negative charges and the higher the surface potential. C‐S‐H gels with a long silicate anion structure exhibited higher adsorption capacity for methylene blue than gels with a short silicate anion structure. The enhanced adsorption capacity of the C‐S‐H gels is related to the higher number of silanol groups in the bridging silica tetrahedra of the intermediate anion chain structure compared with those in the end units of silica tetrahedra.     

Removal of Lead Ions from Aqueous Solutions by Different Types of Industrial Waste Materials: Equilibrium and Kinetic Studies

Abstract

A comparative study of the adsorbents prepared from several industrial wastes for the removal of Pb²⁺ has been carried out. Fertilizer industry waste viz. carbon slurry and steel plant wastes viz. blast furnace (B.F.) slag, dust, and sludge were investigated as low‐cost adsorbents after proper treatment in the present study. The adsorption of Pb²⁺ on different adsorbents has been found in the order: B.F. sludge>B.F. dust>B.F. slag>carbonaceous adsorbent. The least adsorption of Pb²⁺ on carbonaceous adsorbent even having high porosity and consequently greater surface area as compared to other three adsorbents, indicates that surface area and porosity are not important factors for Pb²⁺ removal from aqueous solutions. The adsorption of Pb²⁺ has been studied as a function of contact time, concentration, and temperature. The adsorption has been found to be exothermic, and the data conform to the Langmuir equation. The kinetic results reveal that the present adsorption system follows Lagergren's first order rate equation. Since all three waste products from the steel industry show higher potential to remove lead from water, therefore, it is suggested that these metallurgical wastes can be fruitfully employed as low‐cost adsorbents for effluent treatment containing toxic metal ions.