Deep purification of seawater using a novel zeolite 3A incorporated polyether-block-amide composite membrane

Characterization and biodegradation of ternary blends of lignosulfonate/synthetic zeolite/polyvinylpyrrolidone for agricultural chemistry

This study investigates novel ternary polymer blends based on polyvinylpyrrolidone (PVP) as the matrix in combination with lignosulfonate and synthetic zeolite. The blends were prepared by the casting method, and their properties were analysed by various techniques, i.e. FTIR analysis, differential scanning calorimetry and thermogravimetric analysis, including tests for water solubility and uptake, and determination of adhesion and hardness. The biodegradation of the blends in soil was also evaluated, and an experiment was conducted on plant growth (Sinapis alba). Optical microscopy showed that particles of the synthetic zeolite were relatively evenly distributed in the polymer matrix, forming random networks therein. The FTIR spectra for the blends proved that hydrogen bonding interactions had occurred between the PVP/synthetic zeolite and PVP/lignosulfonate. DSC analysis confirmed the good miscibility of the PVP and lignosulfonate. TGA results indicated that the thermal stability of the PVP was maintained. Lignosulfonate had the effect of reducing the adhesion of the blends. However, it was revealed that effect depends greatly on the presence of zeolite and the concentration of lignosulfonate. The obtained results showed that the optimal composition of the blend is 2.5 wt% of zeolite and 5 wt% of lignosulfonate into the PVP. Its water solubility and uptake was satisfactory from the perspective of handling and further utilization. A respirometric biodegradation test confirmed that the ternary blend was environmentally friendly, in addition to which a germination experiment evidenced that the lignosulfonate and synthetic zeolite promoted the root growth and development of S. alba. From these findings it was concluded that the novel ternary polymer blend was applicable as either as seed carriers (in the form of seed tapes) or as a biocompatible coating to protect seeds.

Silicalite-1/PDMS Hybrid Membranes on Porous PVDF Supports: Preparation, Structure and Pervaporation Separation of Dichlorobenzene Isomers

Separation of dichlorobenzene (DCB) isomers with high purity by time− and energy−saving methods from their mixtures is still a great challenge in the fine chemical industry. Herein, silicalite-1 zeolites/polydimethylsiloxane (PDMS) hybrid membranes (silicalite-1/PDMS) have been successfully fabricated on the porous polyvinylidene fluoride (PVDF) supports to first investigate the pervaporation separation properties of DCB isomers. The morphology and structure of the silicalite-1 zeolites and the silicalite-1/PDMS/PVDF hybrid membranes were characterized by XRD, FTIR, SEM and BET. The results showed that the active silicalite-1/PDMS layers were dense and continuous without any longitudinal cracks and other defects with the silicalite-1 zeolites content no more than 10%. When the silicalite-1 zeolites content exceeded 10%, the surfaces of the active silicalite-1/PDMS layers became rougher, and silicalite-1 zeolites aggregated to form pile pores. The pervaporation experiments both in single-isomer and binary−isomer systems for the separation of DCB isomers was further carried out at 60 °C. The results showed that the silicalite-1/PDMS/PVDF hybrid membranes with 10% silicalite-1 zeolites content had better DCB selective separation performance than the silicalite-1/α−Al2O3 membranes prepared by template method. The permeate fluxes of the DCB isomers increased in the order of m−DCB < o−DCB < p−DCB both in single-isomer and binary-isomers solutions for the silicalite-1/PDMS/PVDF hybrid membranes. The separation factor of the silicalite-1/PDMS/PVDF hybrid membranes for p/o−DCB was 2.9 and for p/m−DCB was 4.6 in binary system. The permeate fluxes of the silicalite-1/PDMS/PVDF hybrid membranes for p−DCB in p/o−DCB and p/m−DCB binary−isomers solutions were 126.2 g∙m−2∙h−1 and 104.3 g∙m−2∙h−1, respectively. The thickness−normalized pervaporation separation index in p/o−DCB binary−isomers solutions was 4.20 μm∙kg∙m−2∙h−1 and in p/m−DCB binary−isomers solutions was 6.57 μm∙kg∙m−2∙h−1. The results demonstrated that the silicalite-1/PDMS/PVDF hybrid membranes had great potential for pervaporation separation of DCB from their mixtures.

Effective desalination of brackish groundwater using zeolitized diatomite/kaolinite geopolymer as low-cost inorganic membrane; Siwa Oasis in Egypt as a realistic case study

The salinization of the groundwater wells in Siwa oasis, Egypt represents a critical environmental and economic issue. Developing low-cost, effective, and self-supported inorganic membranes were suggested as suitable desalination techniques. Zeolite/geopolymer (Z/GP) membrane was synthesized as a potential low-cost membrane for effective desalination of brackish groundwater in Siwa Oasis, Egypt. The membrane was synthesized by simple geopolymerization for natural kaolinite and diatomite at room temperature. This was followed by hydrothermal growth of zeolite at 100 °C for 24 h to produce zeolitized geopolymer as potential inorganic membrane. After that, the prepared membrane was incorporated in the pervaporation desalination system considering the effect of the membrane thickness and the temperature. The results demonstrated water flux values of 8.34 kg.m^-2.h^-1, 7.63 kg.m^-2.h^-1, and 7.05 kg.m^-2.h^-1 for the tested membrane at thicknesses of 1 mm, 2 mm, and 3 mm, respectively. This associated with significant salt rejection prearranges 95.8% (1 mm), 97.6% (2 mm), and 99.4% (3 mm). Moreover, the high-temperature value (90 °C) is of strong positive impact on the water flux (7.82 kg.m^-2.h^-1) and a slight impact on the salt rejection (99.6%). The membrane is of significant stability considering the obtained water flux (7.51 kg.m^-2.h^-1) and salt rejection (99.57%) after 130 h. The reusability properties of the Z/GP membrane demonstrated its suitability to be used in the desalination process for five runs. Therefore, the synthetic Z/GP membrane is a highly recommended product for simple, effective, low cost, and available desalination technique brackish groundwater in Siwa Oasis.

Produced Water Desalination via Pervaporative Distillation

Herein, we report on the performance of a hybrid organic-ceramic hydrophilic pervaporation membrane applied in a vacuum membrane distillation operating mode to desalinate laboratory prepared saline waters and a hypersaline water modeled after a real oil and gas produced water. The rational for performing “pervaporative distillation” is that highly contaminated waters like produced water, reverse osmosis concentrates and industrial have high potential to foul and scale membranes, and for traditional porous membrane distillation membranes they can suffer pore-wetting and complete salt passage. In most of these processes, the hard to treat feed water is commonly softened and filtered prior to a desalination process. This study evaluates pervaporative distillation performance treating: (1) NaCl solutions from 10 to 240 g/L at crossflow Reynolds numbers from 300 to 4800 and feed-temperatures from 60 to 85 °C and (2) a real produced water composition chemically softened to reduce its high-scale forming mineral content. The pervaporative distillation process proved highly-effective at desalting all feed streams, consistently delivering <10 mg/L of dissolved solids in product water under all operating condition tested with reasonably high permeate fluxes (up to 23 LMH) at optimized operating conditions.

Structures, Properties, and Performances-Relationships of Polymeric Membranes for Pervaporative Desalination

For the fulfilment of increasing global demand and associated challenges related to the supply of clean-and-safe water, PV has been considered as one of the most attractive and promising areas in desalinating salty-water of varied salinities. In pervaporative desalination, the sustainability, endurance, and structural features of membrane, along with operating parameters, play the dominant roles and impart paramount impact in governing the overall PV efficiency. Indeed, polymeric- and organic-membranes suffer from several drawbacks, including inferior structural stability and durability, whereas the fabrication of purely inorganic membranes is complicated and costly. Therefore, recent development on the high-performance and cost-friendly PV membrane is mostly concentrated on synthesizing composite- and NCP-membranes possessing the advantages of both organic- and inorganic-membranes. This review reflects the insights into the physicochemical properties and fabrication approaches of different classes of PV membranes, especially composite- and NCP-membranes. The mass transport mechanisms interrelated to the specialized structural features have been discussed. Additionally, the performance potential and application prospects of these membranes in a wide spectrum of desalination and wastewater treatment have been elaborated. Finally, the challenges and future perspectives have been identified in developing and scaling up different high-performance membranes suitable for broader commercial applications.