A subcritical water treatment method was developed for preparing porous-surfaced glass beads with an egg-shell structure in a batch reactor. Based on the ＂corrosion-ion-migration-recondensation＂ strategy, ordinary soda-lime glass beads with a diameter of about 100 um were made first to react with subcritical water to effect controlled quantity of silicate dissolution of glass by adjusting treatment time and temperature. The dissolved silicate was then made to recondense on the glass core to form different porous shell morphologies： pores, flakes and fibers. Among these, glass beads coated with fibers with surface area of 154.5 m2/g, pore volume of 0.27 cm3/g and pore size of 7.1 nm were obtained at 573 K after 2 h of treatment. The prepared porous-surfaced glass beads were then used as adsorbent for heavy metal ions, showing various ion exchange properties. Glass beads covered with fibers displayed fast kinetics and high sorption capacity because of their egg-shell structure and high surface area. More than 90% of copper ions were adsorbed within 100 min from a solution with an initial concentration of 110 mg/L at 313 K. Ion sorption capacities were 149.33, 81.33 and 42.96 mg/g respectively for Ag＋, Cu2＋ and Ni2＋ at 313 K. A green and low-cost method was thus developed to produce egg-shell-structured porous glass with high sorption capacity.
Chun ShenYujun WangJianhong XuYangcheng LuGuangsheng Luo
Synthesizing epichlorohydrin(ECH) from dichloropropanol(DCP) is a complicated reaction due to the partial decomposition of ECH under harsh conditions. A microchemical system can provide a feasible platform for improving this process by conducting a separation once full conversion has been achieved. In this work, referring to a common DCP feed used in industry, the reaction performance of mixed DCP isomers with Na OH in the microchemical system on various time scales was investigated. The operating window for achieving high conversion and selectivity was on a time scale of seconds, while the side reactions normally occurred on a time scale of minutes. Plenty of Cl-ions together with a high temperature were proved to be critical factors for ECH hydrolysis.A kinetic study of alkaline mediated ECH hydrolysis was performed and the requirements for an improved ECH synthesis were proposed by combining quantitative analysis using a simpli fied reaction model with experimental results on the time scale of minutes. Compared with the conventional distillation process, this new strategy for ECH synthesis exploited microchemical system and decoupled the reaction and separation with potentials of higher productivity and better reliability in scaling up.
Si/Al composite hollow spheres with a surface hole were prepared with the co-axial microchannel in a one-step method. It is easy to use the technique for size control and continuous operation. At Si/Al ratio between 4 and 5, a hole forms on the surface, due to the fast gelation process and high viscosity of the sol. Scanning electron microscopy, nitrogen adsorption–desorption isotherms, and mercury intrusion method are used to characterize the samples. The hole size is 40–150 μm and the particle size is 450–600 μm. The size can be adjusted by the flow rate of the oil phase.
