Well-defined rodlike and fiberlike SBA-15 mesoporous silicas have been selectively synthesized from an aqueous reaction mixture consisting of a commercial sodium silicate solution, P123 triblock copolymer and HCl. The morphologies and physicochemical properties of the products were found to be greatly affected by the shearing stress exerted by cylindrical silicated-surfactant micelles in a flowing solution, referred to hereafter as "shearing flow". Monodispersed rodlike particles ca. 0.5-µm wide and ca. 1-2-µm long were formed under static reaction conditions, whereas continuous stirring of the reaction mixture led to the formation of fiberlike silicas with lengths of several hundred micrometers and a relatively uniform width of ca. 10 µm. The effects of the synthesis conditions, such as the initial ratio of the reactants, time, temperature, and the acid source, in addition to shearing flow, on particle morphologies were investigated. Fiberlike silicas of various lengths were obtained from a relatively wide range of synthesis conditions, while monodispersed rodlike silicas were prepared under very specific conditions. Each fiberlike product was found to be comprised of a bundle of fibers, with each fiber formed by the coupling of rodlike particles of almost identical size, irrespective of different synthesis conditions.
The dynamic adsorption/desorption behavior of volatile organic compounds (VOCs) such as toluene (C7H8) and benzene (C6H6) was evaluated for three kinds of mesoporous silicas of SBA-15, all having almost the same mesopore size of ca. 5.7 nm, and a MCM-41 silica with a smaller pore size of 2.1 nm using a continuous three-step test. The fiberlike SBA-15 silica exhibited exceptionally good breakthrough behavior, a higher VOC capacity, and easier desorption. The fiberlike silica was composed through the catenation of rodlike particles. The rodlike silicas, by comparison, were proven to be less useful in dynamic adsorption processes because of lower dynamic VOC capacities despite having comparative porous parameters with the fiberlike silica. The large dynamic VOC capacity of the fiberlike silica was attributed to the presence of a bimodal pore system consisting of longer, one-dimensional mesopore channels connected by complementary micropores.
The thermal plasma inflight processing of electroplating sludge was investigated. Elimination of the heavy metals chromium, nickel, copper, and zinc from the sludge and conversion of the residual sludge into inert slag were achieved. The thermal plasma inflight treatment of the sludge was accomplished with various plasma gas compositions and different specific energies. Heavy metals in the form of ferrite/chromite [(Ni, Zn, Fe)(Fe, Cr) 2 O 4 ] were identified by X-ray diffraction. DC plasma experiments revealed that N 2 -O 2 plasma yielded the highest elimination rate of heavy metals for the given experimental conditions. The influence of the heat transfer rate on the elimination rate of heavy metals was investigated by comparing results from dc and RF plasma experiments. Except for Ni, leaching of heavy metals from deposits prepared by H 2 plasma treatment was minimal.
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