This research summarises the results of the study on the removal of chromium by applying the ferrite process to the solutions obtained from two different Cr(VI) reduction processes utilising sodium sulphite and ferrous sulphate as reducing agents. For both solutions containing trivalent chromium ions, the optimum treatment conditions were determined. The generated sludges were characterised by XRD analysis and physical tests. In addition, to explore the dissolution properties of the sludges obtained, they were contacted with the solutions of sulphuric, citric, tartaric, oxalic and ascorbic acids and EDTA. Also, the sludge samples were subjected to standard toxicity characterisation leaching procedure (TCLP) test of USEPA in order to determine the pollution potential. An efficient Cr(III) removal (about 100%) in the solution from the Cr(VI) reduction process utilising sodium sulphite as reducing agent was achieved when the solution was treated at pH 9 and 50 degrees C for 60 min in the presence of Fe2+/Cr3+ weight ratio of 16. For the other Cr(III) solution prepared from Cr(VI) reduction by ferrous sulphate, a Fe2+/Cr3+ weight ratio of 17.9 at the same conditions was found to produce complete removal of Cr(III). It was determined that the spynel chromium-iron compounds obtained in the process were in the form of chromite (Cr2FeO4). Dissolution experiments and TCLP tests show that the concentrations of the chromium dissolved from both sludges were below the limit given as 5 mg l(-1) by USEPA. The results showed that Cr(III) removal through ferrite process provides the advantages that the sludges generated are non-voluminous, easily separable and environmentally stable. 相似文献
A comparative study of two pre-stressed girder bridges, one with AASHTO (American Association of State Highway and Transportation Officials) Type III girders and the other with new FIB (Florida l-beam) girders, is presented. FIB girders are expected to provide increased lateral stiffness, higher load carrying capacity, cost-efficiency and better reliability. In this paper, the first bridge that is analyzed is a 3-span bridge designed with six AASHTO Type III girders, and the second bridge has four FIB girders with the same span length, width and girder depth. The bridges are analyzed for Florida state legal loads SU4 and C5. Both bridges are analyzed using a sophisticated finite element method. The deflections, moment envelopes, section capacity and live load rating of the two bridges are obtained and compared. FIB girders have higher vertical stiffness, higher section capacity providing higher load rating than the AASHTO girders. 相似文献
In this study, the 1.0 m H2SO4 solution was used as a sulphur source to sulphurise apricots. Apricot samples were immersed into 1.0 m H2SO4 solution at room temperature for time of 30, 60 , 120, 180 and 240 min. Amounts of vitamins (A, C and E) and malondialdehyde (MDA) were determined as function of sulphurisation time and thus, sulphur content. It was determined that the optimum immersion time for sufficient sulphur content is 120 min. It is concluded that while amounts of vitamins decrease, the level of MDA increases with increasing immersion time and thus, sulphur contents. 相似文献
An efficient distributed algorithm for evaluating an iterative function on all pairwise combinations of C objects on an SIMD hypercube is presented. The algorithm achieves uniform load distribution and minimal, completely local interprocessor communication. 相似文献
Aniline derivatives were diazotized and coupled with 3-aminocrotononitrile to give the corresponding 2-arylhydrazono-3-ketiminobutyronitriles. Cyclization of these arylhydrazono derivatives with hydrazine monohydrate afforded 5-amino-4-arylazo-3-methyl-1H-pyrazoles which were subsequently diazotised and coupled with malononitrile to yield a series of pyrazolylhydrazonomalononitriles. These compounds were then reacted with hydrazine monohydrate to provide 10, novel, heterocyclic disazo dyes, which were characterized by elemental analysis and spectral methods. The antimicrobial activity and absorption characteristics of the dyes were also examined in detail. 相似文献
Vinegar fermentation wastewater with different initial COD contents (9.66–48.6 g L−1) were used for hydrogen gas production with simultaneous COD removal by electro-hydrolysis. The applied DC voltage was constant at 4 V. The highest cumulative hydrogen production (3197 ml), hydrogen yield (2766 ml H2 g−1 COD), hydrogen formation rate (799 ml d−1), and percent hydrogen (99.5%) in the gas phase were obtained with the highest initial COD of 48.6 g COD L−1. The highest energy efficiency (48%) was obtained with the lowest COD content of 9.66 g L−1. Hydrogen gas production by water electrolysis was less than 250 ml and wastewater control resulted in less than 25 ml H2 in 96 h. The highest (12%) percent COD removal was obtained with the lowest COD content. Hydrogen gas was produced by reaction of (H+) ions present in raw WW ( pH = 3.0) and protons released from acetic acid with electrons provided by electrical current. Electro-hydrolysis of vinegar wastewater was proven to be an effective method of H2 gas production with some COD removal. 相似文献
Two series samples of Iron Oxide nanoparticles doped with nickel and cobalt with different doping values (x?=?0.01; 0.03; 0.05 and 0.07), were successfully synthesized by using sol–gel method, and then they were characterized by X-ray diffraction, scanning electron and vibrating sample magnetometer (VSM). X-ray diffraction analysis of two series samples showed the formation α-Fe2O3 nanoparticles, accompanied by two phases iron spinels, CoFe2O4 and NiFe2O4. In addition, the variations in grain size were observed for both two series. The observation by scanning electron microscopy reveals a change in the morphology of the grains of all the samples doped, which confirm the cobalt and nickel effect on the morphology of iron oxide nanoparticles. Magnetic measurements which were measured by VSM showed significant magnetic parameters such as coercivity and magnetization besides the ferromagnetic behavior of both two series doped with Cobalt and Nickel.
A novel rotating brush biofilm reactor (RBBR) was used for para-chlorophenol (4-chlorophenol, 4-CP), COD and toxicity removal from synthetic wastewater containing different concentrations of 4-CP. Effects of major operating variables such as the feed 4-CP and COD concentrations and A/Q (biofilm surface area/feed flow rate) ratio on the performance of the biofilm reactor were investigated. A Box-Wilson statistical experiment design method was used by considering the feed 4-CP (0-1000 mg l(-1)), COD (2000-6000 mg l(-1)) and A/Q ratio (73-293 m(2) day m(-3)) as the independent variables while the 4-CP, COD and toxicity removals were the objective functions. The results were correlated by a response function and the coefficients were determined by regression analysis. Percent 4-CP, COD and toxicity removals determined from the response functions were in good agreement with the experimental results. 4-CP, COD and toxicity removals increased with decreasing feed 4-CP and increasing A/Q ratio. Optimum conditions resulting in maximum COD, 4-CP and toxicity removals were found to be A/Q ratio of nearly 180 m(2) day m(-3), feed COD of nearly 4000 mg l(-1) and feed 4-CP of less than 205 mg l(-1). 相似文献
STDMA emerges as a promising channel access technique for providing Quality of Service (QoS) guarantees in multi-hop ad hoc
networks such as community mesh and sensor networks. The contention-free channel access combined with spatial reuse of the
channel provide significant benefits in the energy/throughput trade-off. On the other hand, the time-multiplexed communication
introduces extra delay on the packets when relayed by intermediate nodes. Hence in large wireless sensor networks or mesh
networks, where data is routed over several hops before reaching the data sink, STDMA protocols may introduce high end-to-end
latency due to the reservation-based access policy. We argue that a suitable routing protocol specifically designed for reservation-based
Medium Access Control (MAC) protocols can alleviate their high-latency drawback. Following this argument, we propose first
such routing algorithms working on top of a generic STDMA MAC protocol. First, we consider routing with data fusion and present
our GreenWave routing idea. We show that our algorithm significantly reduces the end-to-end delay when compared to routing
over the shortest-hop paths. Second, we consider routing without data fusion, by taking into account the effect of congestion
along the paths on the end-to-end delays. We provide a QIP formulation of the problem, and present a lower bound and a heuristic
algorithm to bound the optimal solution. Based on the centralized heuristic algorithm, we propose a distributed, dynamic routing
protocol GreenWave routing with Congestion and Flow control (GWCF), which uses a novel congestion and flow control technique utilizing the underlying contention-free protocol. We show by simulations
that GWCF routing significantly improves the end-to-end delay while increasing the network throughput when compared to routing
over shortest paths.