Improving membrane filtration performance through time series analysis

For ultrafiltration, and membrane filtration more generally, the quantitative determination of the modes of fouling remains a subject of great interest. Herein an integral method for determining the modes from a time series of volumetric flux $$J\left(t\right)$$ J t is given and illustrated with previously published filtration data of bergamot juice (Ruby-Figueroa et al (J Membr Sci 524:108-116, 2017)). The integral method of fouling analysis has the potential to become the cornerstone of a robust empirical process. In addition to determining, in a clear-cut manner, the point at which there is a switch from one mode to another, the robust methodology yields characteristic $$J\left(t\right)$$ J t equation for each mode that are an excellent fit to the data. The emphasis is upon the creation of a robust methodology which is best viewed as being a semi-empirical method that is indicative of the modes of fouling. For the example chosen, the initial 4 L/m2 generates some pore blocking after which the main mode of fouling is cake build-up. The variation of overall resistance with time is also informative and analysis of this series was used to check the result for the initial phase of fouling as determined from the time series of volumetric flux. A comparison against the ARIMA (Autoregressive integrated moving average) method, which has never been previously undertaken, is given herein. The integral method of fouling analysis was found to be superior, in part because of the quality of fit to the data and in part because it enables one to establish whether the initial fouling is different in character from the subsequent fouling. Having this information can improve membrane selection and overall membrane filtration performance.

Reverse osmosis and forward osmosis fouling: a comparison

Our previously reported exploration (Journal of Membrane Science 565 (2018) 241–253) on the differences between fouling in reverse osmosis (RO) and forward osmosis (FO), used alginate as a foulant with initial conditions that ensured that the starting fluxes were the same. That study found that for a cellulose triacetate (CTA) membrane the extent of fouling, based on the analysis of foulant resistance, was greater when the membrane was part of a FO system. Herein, using the same methodology, results for a thin film composite membrane with alginate as the foulant are presented and these confirm the same general conclusion namely that the extent of foulant accumulation in FO mode is more severe than in RO mode. Furthermore the specific fouling resistance with alginate fouling in FO is more than for RO. However examining the overall operation including cleaning as well as fouling, this study suggests that FO operation is potentially less sensitive to fouling phenomena than RO for similar feed materials. This is due to the driving force compensation coming from a changing level of ICP. Some preliminary work including that with silica particles is also reported.

Green anionic polymerization of vinyl acetate using Maghnite-Na+ (Algerian MMT): synthesis characterization and reactional mechanism

In this work, the green polymerization of vinyl acetate is carried out by a new method which consists in the use of clay called Maghnite-Na+ as an ecological catalyst, non-toxic, inexpensive and recyclable by simple filtration. X-ray diffraction (XRD) showed that Maghnite-Na+ is successfully obtained after cationic treatment (sodium) on raw Maghnite. It is an effective alternative to replace toxic catalysts such as benzoyl peroxide (BPO) and Azobisisobutyronitrile (AIBN) which are mostly used during the synthesis of polyvinyl acetate (PVAc) making the polymerization reaction less problematic for the environment. The synthesis reaction is less energetic by the use of recycled polyurethane as container for the reaction mixture and which is considered as a renewable material and a good thermal insulator which maintains the temperature at 0 °C for 6 h. The reaction in bulk is also preferred to avoid the use of a solvent and therefore to stay in the context of green chemistry. In these conditions, the structure of obtained polymer is established by Nuclear Magnetic Resonance Spectroscopy 1H NMR and 13C NMR. Infrared spectroscopy (FT-IR) is also used to confirm the structure of PVAc. Thermogravimetric analysis (TGA) showed that it is thermally stable and it starts to degrade from 330 °C while Differential Scanning calorimetry (DSC) shows that this polymer has a glass transition temperature (Tg = 50 °C). The composition in PVAc/Maghnite-Na+ (7 wt% of catalyst) is the most tensile resistant with a force of 182 N and a maximum stress of 73.16 MPa, the most flexible (E = 955 MPa) and the most ductile (εr = 768%).

Steam gasification of municipal solid waste for hydrogen production using Aspen Plus® simulation

Approximately 50 million ton of municipal waste is generated in Pakistan per annum and most of this waste does not reach final deposit sites. In this research, Silvia gas technology for municipal solid waste (MSW) steam gasification is studied to produce high energy density product gas. A detailed simulation model is developed with the help of Aspen Plus®. Catalyst coal bottom ash along with lime (CaO) as sorbent is employed for tar reduction and improving the hydrogen (H2) yield in the product gas. The effect of gasification operating temperature and the ratio of steam to feedstock on synthetic gas composition, hydrogen (H2) yield and heating values of synthesis gas was studied. Coal bottom ash along with CaO had a substantial effect on hydrogen (H2) yield and synthesis gas production. Rise in steam–MSW ratio increased the hydrogen (H2) from 58 to 74.9% (vol.). The maximum value of hydrogen (H2) production, i.e., 74.9% by vol. was achieved at a steam–feedstock ratio of 1.9. A maximum of 79.8% by vol. hydrogen (H2) was attained at 680 °C gasification operating temperature with 1.3 ratio of steam to feedstock and coal bottom ash 0.07% by wt. High value of 13.1 MJ/Nm3 of hydrogen-rich synthetic gas was achieved at 680 °C. The acquired results lay the foundation for the economic feasibility study and pilot plant for MSW usage for hydrogen production.

Validation of MATLAB algorithm to implement a two-step parallel pyrolysis model for the prediction of maximum %char yield

Numerical modeling of biomass pyrolysis is becoming a cost and time-saving alternative for experimental investigations, also to predict the yield of the by-products of the entire process. In the present study, a two-step parallel kinetic model was used to predict char yield under isothermal condition. MATLAB ODE45 function codes were employed to solve a set of differential equations that predicts the %char at varying residence times and temperatures. The code shows how the various kinetic parameters and mass of pyrolysis products were determined. Nevertheless, the algorithm used for the prediction was validated with experimental data and results from past works. At 673.15 K, the numerical simulation using ODE45 function gives a char yield of 27.84%. From 573.15 K to 673.15 K, char yield ranges from 31.7 to 33.72% to 27.84% while experimental yield decreases from 44 to 22%. Hence, the error between algorithm prediction and experimental data from literature is − 0.26 and 0.22. Again, comparing the result of the present work with the analytical method from the literature showed a good agreement.

Recent advances in facilitated transport membranes for olefin/paraffin separation

With the development of the petrochemical industry, the demand for light olefins is rapidly increasing. The separation of olefin/paraffin by membrane technology can save energy consumption and improve separation efficiency. This article reviews the latest progress in facilitated transport membranes for olefin/paraffin separation. The separation mechanism and common types of facilitated transport membranes are briefly introduced. Meanwhile, the mechanism of carrier deactivation and the corresponding strategies to improve the stability of the membranes are summarized. In concluding, current developments regarding facilitated transport membranes are summarized and directions for future development are proposed.