CRITICAL FLUX DETERMINATION IN ULTRAFILTRATION OF WASTEWATER FROM A FOOD INDUSTRY BY OPTIMIZATION METHOD

Two ultrafiltration membranes with different geometries (spiral polymeric and tubular ceramic) but similar cutoffs were used to treat wastewater from a food industry. Hydrodynamic conditions were optimized by statistical methods as a strategy to get more accurate values of the critical parameters and then to produce higher water flux and minimization of membrane fouling. The validation of the optimization method was obtained by experimental critical flux determination at critical parameters. Membrane fluxes revealed significant differences during filtration. The polymeric membrane showed an optimal flux of 45.60 Lh^?1 m^?2 at 3.21 bar while operating at a stable time of 11.61 h, whereas optimal flux of the ceramic membrane was 32.43 Lh^?1 m^?2 at 3.98 bar for 16.03 h. Experimental critical flux values were only slightly lower than optimal fluxes for both membranes, showing the validity of the statistics models applied. Negligible osmotic pressure was found on the two membranes at critical flux parameters, indicating irreversible fouling for both cases. The polymeric membrane revealed strong fouling behavior and the ceramic membrane showed a weak form; the flux decline occurred first in the polymeric membrane, whereas the ceramic membrane exhibited high stability during the filtration operations. A high degree of purification of wastewater was obtained by this membrane at critical flux conditions.     

Effect of the length and the volume fraction of wavy steel fibers on the behavior of self-compacting concrete

Self-compacting concrete (SCC) is a highly workable concrete that fills formwork under its own weight (without any vibration or impact). It also passes easily through small spaces between reinforcement bars. The inclusion of fibers in such concrete limits the concrete shrinkage cracks at early age and enhances some of its properties. However, fibers may affect the flow characteristics of SCC. In this paper, three wavy steel fibers (SF) of different lengths, 35, 40, and 50 ± 2 mm with six different volume fractions (V_f) of 0.3, 0.5, 0.8, 1, 1.2, and 1.4% were used in SCC. The experimental results showed that the addition of SF with higher V_f content and longer length decreases the workability of SCC, reduces its passing ability and increases the possibility of blockage. Mechanical performances of concrete in terms of flexural strength and elasticity modulus were improved, where the slightly compressive strength decreased with an increase in V_f content of SF.     

Improvements in surrogate models for process synthesis. Application to water network system design

High accuracy models can be obtained by using different types of surrogate models that accurately approximate equipment phenomenological models and can be used in synthesis problems, leading to faster and more precise solutions. Two types of surrogate models are used to approximate equipment phenomenological models: polynomial and neural network-based. In some cases, these surrogate models are not able to represent more complex equipment. An original methodology to reformulate these models using equations from shortcut equipment design is proposed. A medium-size case study involving fifteen units is presented. The synthesis problem is solved in a short computational time, leading many local solutions. Since several local optima objective function values are very close to each other, the choice of the best configuration among those found should be done qualitatively, because the differences among the objective function values are not significant if compared to the accuracy of equipment cost correlations in the literature.     

Dendrimers or Nanoparticles as Supports for the Design of Efficient and Recoverable Organocatalysts?

The Jørgensen–Hayashi catalyst [(S)‐α,α‐diphenylprolinol trimethylsilyl ether] was grafted onto the surface of two different supports: phosphorus dendrimers (generations 1 to 3) and magnetic, polymer‐coated cobalt/carbon (Co/C) nanobeads. These new supported catalysts displayed high activities and selectivities in the Michael additions of a wide range of aldehydes to different nitroolefins. Moreover, the dendrimer of the third generation displayed excellent recycling abilities since it could be recovered and reused in 7 consecutive runs without loss of activity.     

煤气化废水处理中双侧线汽提塔的应用

针对具有较高pH值的煤气化废水,采用酸性气饱和煤气化废水能降低废水pH值,改善萃取条件后进行萃取。但萃取后的萃余液中存在大量的酸性气、氨和萃取剂。为了回收氨和萃取剂,并脱除酸性气,在原有工作基础上,采用双侧线汽提塔处理萃余液,该塔塔顶分离酸性气,上侧线回收萃取剂,下侧线回收氨。文中是这一建议流程的后续研究工作。通过流程模拟,对影响双侧线汽提塔分离效果的因素,如热进料位置和塔顶采出量、冷热进料比和冷进料温度、上侧线采出位置和采出量、下侧线采出位置和采出量等进行模拟优化。模拟结果显示:双侧线汽提塔可满足塔釜水净化的要求,且有效地分离酸性气、氨和萃取剂,最大程度地回收氨和萃取剂,初步证明了双侧线汽提塔工艺的可行性。     

催化湿式氧化技术处理甲醇制汽油的废水研究

甲醇制汽油是非石油资源合成技术中关键的一项工作,该工艺过程中产生大量的废水。采用高压釜作为反应器,以催化湿式氧化技术对甲醇制汽油（MTG）废水进行处理,催化剂为实验室制得的钌/铈锆复合氧化物催化剂,考察了反应温度、催化剂投加量、反应时间和搅拌转速对废水COD去除率的影响,结果表明,在反应温度240℃、催化剂投加量10 g/L、搅拌转速300 r/min的反应条件下,反应2 h后废水COD去除率达到98.68%。     

COD and AOX Removal and Biodegradability Assessment for Fenton and O3/UV Oxidation Processes: A Case Study from a Graphical Industry Wastewater

Due to process stability and excellent effluent quality, the use of membrane processes is rapidly expanding. However, a drawback is the production of concentrates and their proper disposal. In this study, reverse osmosis concentrate was treated by Fenton and O₃/UV oxidation processes. The concentrate contains halogenated compounds, recalcitrant COD and low biodegradability. The removal of halogenated compounds and the enhancement of biodegradability were examined. Comparing the investigated processes, Fenton oxidation resulted in a better mineralization of organic matter; however, O₃/UV oxidation achieved a better enhancement of the biodegradability. Furthermore, similar degradation of halogenated compounds were observed for both oxidation processes.     

Degradation of an Azo Dye (Ponceau 4R) and Treatment of Wastewater from a Food Industry by Ozonation

Experiments for degradation of the extensively marketed Ponceau 4R dye in aqueous solution and for oxidation of raw wastewater from a confectionary industry have been carried out by using ozone. All the experiments were performed in a cylindrical semi-batch reactor at approximately 20 ^oC for 7200 s. A mass flow rate of 1.158?×?10^?6 kg s^?1 of ozone was continuously fed in the reactor. The pH of the azo dye aqueous solution (distilled water + Ponceau 4R) was always kept at approximately 5.8, while in the case of the raw wastewater the same factor was changed from 4.7 to 9.4 in two different experimental runs. Absorbance measurements at 508 nm show that the investigated azo dye found in the azo dye aqueous solution was completely degraded after only 600 s. At this initial period a substantial fall of TOC (Total Organic Carbon) (up to 45%) was noticed, but the rate was exponentially decreased at longer reaction times up to a TOC removal no higher than 60%. The ozonation was also responsible for reducing the apparent color of the raw wastewater to almost 10% of its initial value at the optimum pH (9.4 ± 1.5). The effect of pH was important on apparent color, but it had absolutely no influence on the kinetics results of COD (Chemical Oxygen Demand), which were kept constant over the entire period of reaction.     

超临界水在降解废弃物及资源化中的应用

综述了超临界水的特性及其在降解废旧塑料、橡胶、纤维素等废弃物及资源化中的应用现状。与传统热分解方法相比,超临界水可实现对高分子废弃物的快速、有效分解,通过分解反应条件的控制,可以控制产物组成,是一种很有前途的废弃物资源化技术。