Development and calibration of an integrative passive sampler for monitoring VCM in drinking water networks

This paper evaluates the applicability of a new sampling device for monitoring vinyl chloride monomer (VCM) in drinking water networks. This system consists of an adsorbing cartridge filled with a strong adsorbent enclosed between two sheets of polyethylene-polyamide membrane. The passive sampler (PS) combines preconcentration on the cartridge with easy extraction by thermal desorption into a gas chromatograph (GC), coupled with a tandem mass spectrometer (MS/MS). In order to estimate the suitability of the device for this application, samplers were calibrated in a hydraulic pilot under controlled parameters. The influences of temperature, flow velocity and variation of concentration of exposure were then examined. Linear uptake was observed during a VCM exposure of 12 days and the effect of temperature on the sampling rate was evaluated. This sampling device responds to an aquatic environmental contamination and Public Health issue, both by the organic volatile contaminant monitored in this environment, and by the sampling approach, still little used in drinking water networks. It offers a complementary monitoring to the current technique, providing a more representative assessment of the temporal contamination.

EFFECTIVENESS OF THE MEMBRANE USE TECHNOLOGIES FOR PURIFICATION AND CONCENTRATION OF PECTIN EXTRACTS

Для оценки эффективности применения мембранных технологий очистки и концентрирования пектиновых экстрактов исследован процесс микро-, ультра- и нанофильтрации пектиновых экстрактов различной природы. Исследования проводили на стендовой установке для одинарных фильтрующих элементов с использованием керамических мембранных элементов ПС-100М для микрофильтрации, полисульфонамидной мембраны УПМ-20 для ультрафильтрации и полиамидной мембраны ОПМН-П для нанофильтрации. Объектами исследований были пектиновые экстракты, полученные из яблочного и свекловичного сырья методом гидролиза-экстрагирования в кислой среде. Установлено, что одноэтапное концентрирование на керамических трубчатых или половолоконных мембранах не позволяет достичь желаемой степени концентрирования. Поскольку пектиновые вещества представляют собой высокомолекулярные кислые полисахариды с молекулярной массой более 20 кДа и при концентрировании кинематическая вязкость их растворов резко возрастает, экранируя поры мембран, исследована возможность двухэтапной очистки и концентрирования пектиновых экстрактов методом микро- и ультрафильтрации. Установлена высокая производительность процесса микрофильтрации для яблочного и свекловичного пектиновых экстрактов в первые 30 мин. Отмечено, что производительность керамических мембран при микрофильтрации яблочного экстракта в 2,5 раза выше, чем свекловичного, при ультрафильтрационном концентрировании с отсечкой по молекулярной массе 50 кДа – в 2,9 раз. Установлено, что для яблочных пектиновых экстрактов применение на стадии ультрафильтрации полисульфонамидной мембраны УПМ-20 неэффективно вследствие более высокой молекулярной массы яблочного пектина по сравнению со свекловичным. Требуется дополнительная третья стадия – нанофильтрация, обеспечивающая концентрирование пектинового экстракта из яблочных выжимок до содержания сухих веществ 4%. For evaluate the efficiency of membrane technologies for purification and concentration of pectin extracts, the process of micro-, ultra- and nanofiltration of pectin extracts of various nature has been studied. The research were carried out on a stand instrument for single filter elements with use of ceramic membrane elements PS-100M for microfiltration, polysulfonamide membrane UPM-20 for ultrafiltration and polyamide membrane OPMN-P for nanofiltration. The objects of research were pectin extracts obtained from apple and sugar beet raw materials by hydrolysis-extraction in an acid medium. It has been found that one-step concentration on ceramic tubular or hollow fiber membranes does not allow to achieve of the desired degree of concentration. Due to the fact that pectin substances are the high molecular acidic polysaccharides with a molecular mass of more than 20 kDa, and when concentrating, the kinematic viscosity of their solutions increases sharply, screening the membrane pores, the possibility of two-stage purification and concentration of pectin extracts by the micro and ultrafiltration method is studied. The high productivity of the microfiltration process for apple and sugar beet pectin extracts was established in the first 30 min. It was noted that the productivity of ceramic membranes in the process of microfiltration of apple extract is 2,5 times higher than that of sugar beet, and with ultrafiltration concentrating mass molecular weight cutoff of 50 kDa – by 2,9 times. It has been found that for apple pectin extracts the use of the UPM-20 polysulfonamide membrane in the ultrafiltration stage is not effective due to higher molecular mass of apple pectin compared to beet pectin. An additional third stage – nanofiltration is required, which provides the concentration of the pectin extract from the apple material to a solids content of 4%.

Synthesis of Polyamide-Based Microcapsules via Interfacial Polymerization: Effect of Key Process Parameters

Polyamide microcapsules have gathered significant research interest during the past years due to their good barrier properties; however, the potential of their application is limited due to the fragility of the polymeric membrane. Fully aliphatic polyamide microcapsules (PA MCs) were herein prepared from ethylene diamine and sebacoyl chloride via interfacial polymerization, and the effect of key encapsulation parameters, i.e., monomers ratio, core solvent, stirring rate and time during the polymerization step, were examined concerning attainable process yield and microcapsule properties (shell molecular weight and thermal properties, MC size and morphology). The process yield was found to be mainly influenced by the nature of the organic solvent, which was correlated to the diffusion potential of the diamine from the aqueous phase to the organic core through the polyamide membrane. Thus, spherical microcapsules with a size between 14 and 90 μm and a yield of 33% were prepared by using toluene as core solvent. Milder stirring during the polymerization step led to an improved microcapsule morphology; yet, the substantial improvement of mechanical properties remains a challenge.

Pengolahan Minyak Jelantah Menggunakan Membran Poliamida/Titanium Dioksida/Arang Aktif Kulit Durian

Processing of wasted cooking oil uses the photocatalyst method with metal catalysts and zeolites to reduce organic compounds. In this study, researchers used activated charcoal from durian skin and titanium dioxide embedded in a polyamide membrane as an adsorbent which was used as a medium for processing wasted cooking oil. The purpose of this study was to determine the effect of processing used cooking oil using a membrane of polyamide/titanium dioxide/durian peels activated charcoal on changes in the characteristics of wasted cooking oil. Based on the results of research on the processing of wasted cooking oil with a membrane of polyamide/titanium dioxide/activated charcoal from durian peels, there was an increase in water content by 10.21%, a decrease in free fatty acids by 33.75%, a decrease in the peroxide number by 18.33%. Used cooking oil that has passed through the membrane has a decrease in %Transmission for the functional groups of C-H alkenes, C-O esters, and C-H alkanes. In the analysis of the compound content by mass spectrophotometry, it was found that the content of the methyl ester compound with the C17 and C19 chains was close to the composition of the biodiesel constituents.

Ultra-Selective Polyamide Membrane from Metal Organic Framework Assembly Regulated Interfacial Polymerization for Desalination and Water Reuse

While reverse osmosis (RO) is the leading technology to address the challenge of water scarcity through desalination and potable reuse of wastewater, current RO membranes still fall short in rejecting certain harmful constituents from seawater (e.g., boron) and wastewater (e.g., N-nitrosodimethylamine, or NDMA). In this study, we develop an ultra-selective polyamide (PA) membrane via enhancing interfacial polymerization using amphiphilic metal-organic framework (MOF) nanoflakes. In this process, MOF nanoflakes horizontally aligned at the water/hexane interface to accelerate the transport of diamine monomers across the interface and conserve gas bubbles and heat of reaction near the interface. These mechanisms synergistically led to the formation of a crumpled PA nanofilm with an ultrathin intrinsic thickness of ~ 5 nm and a high cross-linking degree of ~ 97%. The resulting PA membrane delivered excellent desalination performance that is beyond the existing upper-bound of perm-selectivity, and exhibited very high rejection (> 90%) of boron and NDMA unmatched by state-of-the-art RO membranes.