Fouling behavior of nanofiltration membrane during the refining treatment of morphlines-dominant reverse osmosis concentrate.

Nanofiltration (NF) has been proven to be with great potential for the separation of morpholines with molecular weight less than 200 Da in refining reverse osmosis concentrate (ROC), but its application is significantly restricted by the membrane fouling, which can reduce the rejection and service time. To enable the long-term operation stability of nanofiltration, this work focuses on the fouling behavior of each substance in the hydrosaline organic solution on nanofiltration membrane, aiming to give insight into the fouling mechanism. To this end, in this work, the effects of salts (i.e NaCl and Na2SO4), organic substances (including N-(2-hydroxypropyl)morpholine(NMH) and 4-morpholineacetate(MHA)) and representative divalent ions (Ca2+ and Mg2+) on the performance and physicochemical properties of DK membrane were systematically investigated. The results show that both salts and organics can induce DK membrane swelling, leading to an increase of the mean effective pore size. After the filtration of Na2SO4-NaCl-H2O, the mean pore size increased by 0.002 nm, resulting in the decrease of the removal ratio of NMH and MHA for 3.82% and 13.10%, respectively. With static adsorption of NMH and MHA, the mean pore size of DK membrane increased by 0.005 and 0.003 nm. The swelling slowed the entrance of more organic molecules into membrane pores. Among them, MHA led to the terrible irreversible pore blocking. As the concentration of Ca2+ increased, gypsum scaling was formed on the membrane surface. During this process, NMH and MHA played different roles, i.e. NMH accelerated the CaSO4 crystallization while MHA inhibited. As a conclusion, the fouling behavior of substances in the high saline organic wastewater on DK membrane were systematically revealed with the fouling mechanisms proposed, which could provide an insightful guidance for membrane fouling control and cleaning in the treatment of high salinity and organic wastewater.

Constructing Cylindrical Nanostructures Via Directional Morphology Evolution Induced by Seeded Polymerization.

Herein, spindle-shaped block copolymer (BCP) nanoparticles are used in seeded polymerization of methyl methacrylate as a novel approach to generating cylindrical nanostructures. The chain-extension of BCP seeds by an amorphous coil-type polymer within the seed core composed of semifluorinated liquid-crystalline blocks triggers the deforming, stretching, and directional growth of the seeds along the long axis, eventually leads to nanorods.

Efficient decontamination of heavy metals from aqueous solution using pullulan/polydopamine hydrogels.

Designing a new adsorbent with recyclability, high efficiency and biodegradability is important for treating heavy metals contamination but remains a severe challenge. In this work, a novel type of hydrogel biosorbents based on pullulan and polydopamine were designed for heavy metal ions removal from aqueous solution. The physicochemical properties of the prepared pullulan/polydopamine (Pu/PDA) hydrogels were fully characterized by thermal gravimetric analysis, Fourier transform infrared spectroscopy, rheology, scanning electron microscopy, swelling and compression tests. We observed that their mechanical strength, pore size, water absorption and retention properties could be nicely controlled by adjusting the PDA concentration in the pre-gel solution. Subsequently, the adsorption ability of designed Pu/PDA hydrogels to Cu2+, Co2+ and Ni2+ was investigated in detail. These hydrogels presented excellent adsorption capability for heavy metal ions and matched well with the pseudo-second-order kinetic model and Freundlich isotherm model. Overall, having tunable physicochemical properties coupled with the high absorption ability for heavy metal ions, these Pu/PDA hydrogels may be a promising strategy for removal of pollutants from aqueous solution.

Facile formation of salecan/agarose hydrogels with tunable structural properties for cell culture.

Salecan polysaccharide produced by Agrobacterium sp. ZX09 is an attractive biopolymer to construct hydrogel scaffolds for cell culture. However, some limitations such as poor mechanical performance, complicated fabrication process and slow gelation times still exist in the biomedical applications of microbial-based salecan polysaccharide hydrogels. Here, a series of polysaccharide hydrogels composed of salecan and agarose with adjustable structural properties are designed. The resultant hybrid salecan/agarose hydrogels exhibit controllable physical and chemical properties including thermal stability, water uptake, mechanical strength and microarchitecture, which can be readily realized with minimum change of the polysaccharide content. Furthermore, cytotoxicity assays reveal that the designed composite hydrogels are non-toxic. More importantly, these hydrogels support cell survival, proliferation, and migration. Together, this work opens up a new avenue to build polysaccharide hydrogel platforms for tissue engineering.

Development of a selective molecularly imprinted polymer-based solid-phase extraction for indomethacin from water samples.

A selective molecularly imprinted solid-phase extraction (MISPE) for indomethacin (IDM) from water samples was developed. Using IDM as template molecule, acrylamide (AM) or methacrylic acid (MAA) as functional monomer, ethylene dimethacrylate (EDMA) as crosslinker, and bulk or suspension polymerization as the synthetic method, three molecularly imprinted polymers (MIPs) were synthesized and characterized with a rebinding experiment. It was found that the MIP of AM-EDMA produced by bulk polymerization showed the highest binding capacity for IDM, and so it was chosen for subsequent experiments, such as those testing the selectivity and recognition binding sites. Scatchard analysis revealed that at least two kinds of binding sites formed in the MIP, with the dissociation constants of 7.8 micromol L(-1) and 127.2 micromol L(-1), respectively. Besides IDM, three structurally related compounds--acemetacin, oxaprozin and ibuprofen--were employed for selectivity tests. It was observed that the MIP exhibited the highest selective rebinding to IDM. Accordingly, the MIP was used as a solid-phase extraction sorbent for the extraction and enrichment of IDM in water samples. The extraction conditions of the MISPE column for IDM were optimized to be: chloroform or water as loading solvent, chloroform with 20% acetonitrile as washing solution, and methanol as eluting solvent. Water samples with or without spiking were extracted by the MISPE column and analyzed by HPLC. No detectable IDM was observed in tap water and the content of IDM in a river water sample was found to be 1.8 ng mL(-1). The extraction efficiencies of the MISPE column for IDM in spiked tap and river water were acceptable (87.2% and 83.5%, respectively), demonstrating the feasibility of the prepared MIP for IDM extraction.

Development of a group selective molecularly imprinted polymers based solid phase extraction of malachite green from fish water and fish feed samples.

A group selective molecularly imprinted solid phase extraction (MISPE) for malachite green (MG) from fish water and fish feed samples was developed. Using MG as template molecule, methacrylic acid as functional monomer, ethylene glycoldimethacrylate as linking agent and bulk polymerization as synthetic method, the molecularly imprinted polymers (MIPs) were synthesized and characterized with rebinding experiment. The Scatchard polt's analysis revealed that the template-polymer system showed the two-site binding behavior with dissociation constants of 0.3194 micromol L(-1) and 15.70 micromol L(-1), respectively. MG and two structurally related compounds, leucomalachite green (LMG) and crystal violet (CV) were employed for selectivity test. The MIPs exhibited the highest selective rebinding to MG, but also displayed 83.0% and 87.5% of cross-reactivity with LMG and CV, demonstrating that MIPs could be used as group recognition sorbents in solid phase extraction. The extraction conditions of MISPE column for MG were optimized. Tap water samples spiked with MG at concentration of 0.5-10 ng mL(-1) were extracted by MISPE column and analyzed by high performance liquid chromatography. The recoveries of MISPE column for MG extraction were found to be 76.8-93.7% with the relative standard deviations of 2.12-10.09%, indicating the feasibility of the prepared MIPs for MG extraction. No detectable MG was observed in one fish farming water sample and two fish feed samples; while the MG concentrations in two pet fishpond water samples were found at 1.50 ng mL(-1) and 0.67 ng mL(-1), respectively.