Humic Acid Solution Research Articles

Photoenhanced heterogeneous reaction of O3 with humic acid: Focus on O3 uptake and changes in the composition and optical property.

Heterogeneous photochemical reaction of O3 with humic acid (HA) under simulated sunlight was performed using a flow tube reactor coupled to an O3 analyzer at ambient pressure. It was confirmed that light significantly enhanced the uptake of O3 on HA. The initial uptake coefficient (γi) and the steady-state uptake coefficient (γss) of O3 under irradiation increased by 1.6 and 3.8 times compared to those in the dark, respectively. The γi and γss on HA varied in the range of 0.76-2.77×10-5 and 1.50-9.55×10-6, respectively, which were dependent on various environmental factors including HA mass, total irradiance, initial O3 concentration, O2 content, temperature, relative humidity (RH) and HA solution pH. Both γi and γss showed linear dependence on the total irradiance (0-2.07×1016 photons/(cm2⋅s)) of the light source, and increased with the HA mass (0-3.2μg/cm2), temperature (278-298K) and HA solution pH (4.0-9.6). However, they showed negative correlations with the initial O3 concentration and O2 content. The γi remained constant in the RH range of 7%-60%, while γss exhibited the maximum value at RH=20%. During the ozonization of HA under irradiation, some functional groups were consumed, including CH2, CH3, aromatic CC, OH, CO, COOH and COO-. HA aged by O3 exhibited a decrease in the mass absorption efficiency (MAE) and a small increase in the absorption Ångström exponent between 300 and 600nm wavelength (AAE300,600), which was ascribed to changes in the composition of HA during the photochemical ozonization process.

Influences of cross-linking agents with different MW on the structure of GO/CNTs layers, membrane performances and fouling mechanisms for dissolved organic matter

This study evaluated the impacts of cross-linking agents with different molecular weight (MW) on the structure of graphene oxide (GO)/carbon nanotubes (CNTs) layers and fouling mechanisms. The GO/CNTs-modified membrane was fabricated by chemical activation and vacuum filtration methods and exhibited excellent stability in antifouling performance and rejection rates. Increasing the external diameter of CNTs and MW of cross-linking agents improved the water flux through enlarging the interlayer spacing of GO/CNTs layers, showing the highest water flux of about 1280 kg/m2h. The large external diameter of CNTs deteriorated the antifouling performance and removal efficiency. The small cross-linking agents, i.e. ethanediamine with 60.1 Da or polyethyleneimine with 600 Da, maintained the regular lamellar structure of GO/CNTs layers, causing the high flux and DOC rejection. However, polyethyleneimine with 1800 Da promoted GO/CNTs aggregation and created non-uniform lamellar structure with high surface roughness, resulting in the severest flux decline and the lowest DOC rejection. The fouling model was also influenced by the MW of cross-linking agents; the small agents caused complete blocking while the large agent caused intermediate fouling for humic acid (HA) solution. The bridging effect of Ca2+ resulted in intermediate fouling for all the membranes in the case of HA + Ca2+ solution.

Efficacy of different primers on growth and yield of tulip (Tulipa gesneriana L.)

Tulip (Tulipa gesneriana L.) is an important and highly valuable flower of the cut flower industry. The most critical step in its cultivation is to break dormancy in order to initiate the growth, especially in tropical and sub-tropical areas of the world. Therefore, the current research was conducted to break bulb dormancy and foster the growth of tulip in Potohar region with the help of different primers. The objective of this study was the selection of best primer at appropriate concentration level to enhance growth, yield and vase life of the flower. Tulip bulbs were treated with different primers: T0 (distilled water), T1 (chitosan @ 5 g/L), T2 (gibberellic acid @ 0.15 g/L), T3 (humic acid 160 g/L), T4 (imidacloprid 19 g/L) and T5 (salicylic acid 0.1 g/L) for 24 hours, respectively. The experiment was laid out using Complete Randomized Design (CRD) with three replications. Statistical results revealed that characteristics including early germination, plant height, number of leaves, stalk length, fresh and dry weight of flower, weight of bulbs, diameter of bulbs and number of daughter bulbs were significantly increased in T2. Whereas, leaf area, diameter of stem and flower was maximum in T0. Plants under T3 showed an increase in chlorophyll content of leaves. While floral characteristics like early formation and opening of flower bud, more number of flowers and vase life were improved in T1. Thus, statistical results showed that priming can effectively help to improve morpho-physiological attributes of tulip.

One-Pot Polymerization of Dopamine as an Additive to Enhance Permeability and Antifouling Properties of Polyethersulfone Membrane.

This paper reports the fabrication of polyethersulfone membranes via in situ hydrogen peroxide-assisted polymerization of dopamine. The dopamine and hydrogen peroxide were introduced into the dope solution where the polymerization occurred, resulting in a single-step additive formation during membrane fabrication. The effectivity of modification was evaluated through characterizations of the resulting membranes in terms of chemical functional groups, surface morphology, porosity, contact angle, mechanical strength and filtration of humic acid solution. The results confirm that the polydopamine was formed during the dope solution mixing through peroxide-assisted polymerization as proven by the appearance of peaks associated OH and NH groups in the resulting membranes. The presence of polydopamine residual in the membrane matric enhances the pore properties in terms of size and porosity (by a factor of 10), and by lowering the hydrophilicity (from 69° to 53°) which leads to enhanced filtration flux of up to 217 L/m2 h. The presence of the residual polydopamine also enhances membrane surface hydrophilicity which improve the antifouling properties as shown from the flux recovery ratio of > 80%.

Effect of spraying with zinc nanoparticles, Humic acid, and adding the mineral fertilizer on the growth of pear seedlings (Hollywood cultivar)

The study was conducted at the Al-Hindiya Gardening Station (Karbala province), To study the effect of spraying 3 levels of nano zinc (0, 2, 4 g.L−1) and two levels of humic acid solution (2, 4 ml.L−1) and adding urea mineral fertilizer at two levels (5, 10 g.seedlings −1) in the growth of pear seedlings, Hollywood cultivar grafted on apricot seedlings. The experiment was conducted according to completely randomized designs with three replicates, and the results were as follows: The treatment of zinc at a concentration of (2 ml.L−1) was significantly higher in all vegetative growth traits that included seedlings length, stem diameter, number of leaves, leaf area, dry material of the plant and leaf content of chlorophyll and zinc and gave the highest averages of 84.20 cm, 7.62 mm, 40.70 leaf.seedling−1, 23.67 2 cm2, 42.28 g, 30.27 spad, 9.71 mg.100 g−1, respectively, by comparison treatment, Where, the treatment with a humic acid concentration of 4 ml. Liters -1 was excelled on the above traits and gave the highest averages amounted to 78.17 cm, 7.04 mm, 41.73 leaf.seedling−1, 23.64 cm 2, 43.53 g, 29.17 spad, 9.34 mg.100 g−1 in respectively compared to the treatment of 2 ml.L−1, the treatment of adding urea mineral fertilizer at the level of (10 gm.seedling−1) was significantly excelled by giving the highest values of all studied vegetative traits amounted to 77.89 cm, 7.18 mm, 39.87 leaf.seedling−1, 22.45 cm 2, 42.19 g, 28.64 spad, 9.39 mg. 100 g −1 respectively Keywords: term, term, term

Noncovalently Functionalized Sulfated Castor Oil-Graphene Oxide-Strengthened Polyetherimide Composite Membranes for Superior Separation of Organic Pollutants and Their Fouling Mitigation.

A novel sulfated castor oil (SCO)-graphene oxide (GO)-strengthened polyetherimide (PEI) membrane was prepared for the first time via phase inversion process for the efficient separation of multiple organic pollutants with superior long-term antifouling stability. X-ray diffraction, attenuated total reflectance-Fourier transfer infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and mechanical strength studies revealed that the SCO and GO were successfully incorporated into the PEI membrane with enhanced mechanical strength. The water flux of the PEI/SCO@GO membrane (410.6 L m-2 h-1) was about 50 times that of bare PEI (7.8 L m-2 h-1) and about 6 times that of PEI/SCO (64.5 L m-2 h-1) membranes. The surface hydrophilicity of the PEI/SCO@GO membrane was significantly increased in terms of the decrease of the water contact angle from 98.5° (bare PEI) to 40.4°. The PEI/SCO@GO membrane separation efficiency was found to be greater than 99.0%, particularly for both the oil-in-water emulsion and the humic acid solution, respectively. Because of the higher flux recovery ratio and the lower total fouling rate of the PEI/SCO@GO membrane, a comprehensive antifouling performance was observed during the long-term foulant filtration cycle analyses. Hence, the incorporation of both SCO and GO into the PEI matrix would render the highly hydrophobic PEI material as the suitable and desirable antifouling membrane toward the treatment of various organic foulants in wastewater.

Using an angular detection photometer (ADP) in analyzing the humic acids coagulation process

This paper presents a simply and novel design of an angular detection photometer (ADP) based on detection of infrared radiation from sources placed at various angles. The device allows for real-time monitoring of the coagulation process in in-situ samples. This paper assesses capabilities of the ADP compared with the standard method of the jar test in optimizing the coagulation process of humic acids in a synthetic raw water solution using Al2(SO4)3. Various parameters affecting the coagulation process were tested. The determined optimal doses were: 2.5, 3.5, 4.0 mg Al/L respectively for the reagent system: coagulation with pH adjustment, with polymers aid and for Al2(SO4)3 only. A 87.6 % reduction in A254 and 86.1 % reduction in A436 in a solution of humic acids using the optimum dose of Al2(SO4)3 at 4 mg of Al/L with pH = 6.95 was observed. Optimal process conditions (dose, pH) determined using an ADP match the parameters determined via the jar test method. Based on the standard deviation (SD) of measurement signal fluctuation, a linear relationship with R2 = 0.84 was observed between the SD and sedimentation time of post-coagulant suspensions. In-situ qualitative studies have shown that macromolecular polymers: anionic and nonionic polyacrylamides exhibit strong flocculation abilities with formation of larger particles, respectively SD = (7.3–10.7) and SD = (9.7–19.7), than the cationic polyacrylamide, SD = (1.4–2.1). It was proved that measurements of particle dispersion, regardless of the angle of incidence of the light beam, are justified in analyzing coagulation and can therefore complement analytical procedures used when optimizing the coagulation process.

IMPACT OF MINERAL AND NANO PHOSPHORUS FERTILIZER FORMS SOME WITH HUMIC ACID APPLICATION ON QUALITY AND QUANTITY OF GIZA 95 COTTON CULTIVARS AS WELL AS SOIL PROPERTIES AND FERTELTITY

Two field experiments were performed in Agricultural Farm of Sids Agricultural Research Station , ARC ,Beni-Suef Governorate , Egypt (lat .290 04N, Long .310 ob E and 30-40 m above the mean sea level) To investigate the possibility of using nano- natural rock P instead of chemical superphsphate along humic acid on productivity of cotton as well as soil properties and fertility . The design of the experiment was split plot design , where humic acid treatments (without , 10kg/fed humic acid as soil application and 2 % foliar spraying twice of humic acid solution) were located in main plot , and phosphorus treatments (without , 15.5 kg P2O5 /fed , 31.0 kg P2O5 /fed and 2% foliar spraying twice of nano rock P solution ) were developed in subplots. The results indicated that soil properties and fertility did not affected by phosphorus treatments, except phosphorus availability ,which positively increased due to 15.5 or 31.0 kg P2O5 /fed as superphosphate .) On the other hand add in 10 kg/fed humic acid improved soil pH, OM,bulk density and soil available water as well as soil available N,P and K after cotton harvest in Foliar spraying of 2% nano rock P had equal effect of additions 31.0 kgP2O5 /fed , where it increased plant height, number of fermiting branches, searlinss % , number of open balls /plot , boll weight , seed indx , seed cotton yield as well as leaf cotton content of N,P,K and chlorophyll A and B. Humic acid application improved the above mentioned growth parameter yields and yield components and life cotton content , except earliness % , where 10 kg/fed humic acid as soil application surpassed added humic acid as foliar spraying. On the other hand lint% and fiber properties did not responded to humic acid or phosphorus application . The result of the interaction showed that the best treatment for Gisaas cotton antiwar production is 2% foliar spraying of nano rock P solution or 31kg/fed P2O5 + 10 kg /fed humic acid as soil application

Surface modification of reverse osmosis membranes by grafting of polyamidoamine dendrimer containing graphene oxide nanosheets for desalination improvement

The use of grafting method by a dendrimer coupling with a nanomaterial in the modification of commercial polyamide reverse osmosis membranes is reported. This study provides the effect of grafting method with a hydrophilic polyamidoamine (PAMAM) dendrimer and graphene oxide (GO) nanosheet to reduce fouling. The response surface method with central composite design (CCD) was used to optimize the input variables of the grafting process, i.e. dendrimer concentration, grafting time and grafting temperature, and the responses of this method included flux, salt retention and antifouling. First, the grafting conditions were optimized and next, different amounts of GO were dispersed in optimum formulation. The modified membranes were tested using humic acid (HA) solution for fouling test and NaCl and NaNO3 solutions for permeability and rejection tests by a cross-flow setup. The results from ATR-FTIR, SEM, AFM, contact angle and zeta potential analyses established successful grafting and modification. The modified PAMAM/GO and PAMAM membranes exhibited less fouling than the commercial reverse osmosis membranes. Among these, the modified membrane with 1.5 wt% PAMAM concentration at 30 °C of grafting temperature and 6 min grafting time with 1 wt% dispersed GO has the least amount of fouling and has the lowest contact angle, the best chlorine resistance; and improved desalination performance in real wastewater treatment.

Reciprocal interference of clay minerals and nanoparticulate zero-valent iron on their interfacial interaction with dissolved organic matter

With increasing environmental application of nanoparticulate zero-valent iron (nZVI), it is essential to explore the interaction of nZVI with dissolved organic matter (DOM) and clay mineral particles (CMPs) and its potential effect on the formation of DOM-mineral complex that may impact the carbon sequestration. The aggregation and adsorption behaviors of nZVIs (two bare nZVIs of different sizes and one carboxymethyl cellulose coated nZVI (CMC-nZVI)) and CMPs (kaolinite and montmorillonite) coexisting in DOM (humic acid and fulvic acid) solutions were systematically investigated. The bare nZVIs more easily formed heteroaggregates with montmorillonite than kaolinite in DOM solutions, while the CMC-nZVI tended to attach on kaolinite surface. The heteroaggregation and competition between nZVIs and CMPs could change their interfacial interaction with DOM and the ultimate immobilization of DOM was determined by the formed nZVI-CMP complexes, irrelevant to the addition sequence of nZVIs and CMPs. Compared with the individual CMPs alone, the formed bare-nZVIs-CMP heteroaggregates promoted the sequestration of DOM especially its aromatic carbon fractions, while the CMC-nZVI had no such effect. These findings will be helpful for the understanding of nZVI interaction with DOM and CMPs and the effect on the immobilization of organic carbon in the environment.

Coupling Persulfate-Based AOPs: A Novel Approach for Piroxicam Degradation in Aqueous Matrices

The activated persulfate degradation of piroxicam, a non-steroidal anti-inflammatory drug (NSAID) belonging to oxicams, was investigated. Persulfate was activated with thermal energy or (UV-A and simulated solar) irradiation. Using 250 mg/L sodium persulfate at 40 °C degraded almost completely 0.5 mg/L of piroxicam in 30 min. Increasing piroxicam concentration from 0.5 to 4.5 mg/L decreased its removal. The observed kinetic constant was increased almost ten times from 0.077 to 0.755 min−1, when the temperature was increased from 40 to 60 °C, respectively. Process efficiency was enhanced at pH 5–7. At ambient conditions and 30 min of irradiation, 94.1% and 89.8% of 0.5 mg/L piroxicam was removed using UV-A LED or simulated solar radiation, respectively. Interestingly, the use of simulated sunlight was advantageous over UV-A light for both secondary effluent, and 20 mg/L of humic acid solution. Unlike other advanced oxidation processes, the presence of bicarbonate or chloride in the range 50–250 mg/L enhanced the degradation rate, while the presence of humic acid delayed the removal of piroxicam. The use of 0.5 and 10 g/L of methanol or tert-butanol as radical scavengers inhibited the reaction. The coupling of thermal and light activation methods in different aqueous matrices showed a high level of synergy. The synergy factor was calculated as 68.4% and 58.4% for thermal activation (40 °C) coupled with either solar light in 20 mg/L of humic acid or UV-A LED light in secondary effluent, respectively.

Photocatalytic facile ZnO nanostructures for the elimination of the antibiotic sulfamethoxazole in water

The degradation of sulfamethoxazole (SMX) by a synthesized ZnO catalyst and under UVA irradiation was examined. ZnO nanostructures were developed by a facile hydrothermal-assisted method. The effect of ZnO heating time and synthesis reaction, pH, catalyst loading, and SMX initial concentration on process efficiency was studied. Water matrices, such as humic acid (HA) solution and surface water (SW), were also used to resemble real environmental water samples. It was observed that when ZnO is synthesized at pH 7.5, nanorods grow on its surface, while nanoplatelets are formed when synthesis takes place at pH 12.5. SMX removal reached 84% after 60 min of treatment in the presence of 200 mg/L ZnO catalyst (8 h-heated at pH 7.5; C0 = 10 mg/L). The pseudo-first-order kinetic constants of SMX photodegradation were calculated at 0.039, 0.030 and 0.016 min−1 for 5, 10, and 20 mg/L SMX, respectively. This decreased efficiency was attributed to the excessive coverage of catalyst surface by SMX molecules, evidenced by SEM micrographs produced after treatment. SMX degradation in SW (12.5%) was considerably lower than in UPW (47.4%) due to the presence of natural organic matter in the first. Interestingly, SMX removal was greatly enhanced in HA matrix (99%) and this can be attributed to the ability of HA to sensitize colloidal ZnO. In all cases, morphological changes of ZnO nanostructures were observed after photocatalytic treatment. It was confirmed that SMX degradation takes place through HO by adding HO quenchers, such as tert-butyl alcohol and methanol, in the reactant mixture.

Tailored CNTs Buckypaper Membranes for the Removal of Humic Acid and Separation of Oil-in-Water Emulsions.

Carbon nanotubes (CNTs) are a robust material and proven as a promising candidate for a wide range of electronic, optoelectronic and environmental applications. In this work, two different methods were utilized for the preparation of CNTs exhibiting different aspect ratios via chemical vapor deposition (CVD). The as-prepared CNTs were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2adsorption isotherms, thermogravimetric analysis and Raman spectroscopy in order to investigate their morphological and structural properties. Free-standing CNTs “buckypaper” membranes were fabricated, characterized and tailored to meet the requirements of two applications, i.e., (1) the removal of humic acid (HA) from water and (2) separation of oil-in-water emulsions. It was revealed that the hydrophobic buckypapers showed high separation performance for Shell oil-in-water emulsions filtration, with up to 98% through the accumulation of oil droplets onto the membrane surface. The absorption capacity of buckypaper membranes for various organic liquids (oil, chloroform and toluene) was evaluated over 10 absorption cycles to investigate their recyclability and robustness. Moreover, surface modification was introduced to the pristine CNTs to increase their surface hydrophilicity and improve the pure water permeability of buckypapers. These modified buckypapers showed high flux for HA solutions and excellent HA rejection efficiency up to 95%via size exclusion and electrostatic repulsion mechanisms.

Preparation of Fe3O4@TiO2 blended PVDF membrane by magnetic coagulation bath and its permeability and pollution resistance

Fe3O4@TiO2 magnetic photocatalytic particles were synthesized and characterized. A composite PVDF separation membrane blended with Fe3O4@TiO2 particles was prepared by the phase inversion method. The main purpose was to explore the effect of magnetic fields on the performance of membranes during coagulation bath. The structure characterization, permeability, interception ability, and anti-pollution performance of inorganic particle blend membranes were then tested. Results showed that magnetic field coagulation baths have little effect on the pore structure and hydrophilicity of the membrane surface. When the liquid membranes was condensed under a magnetic field, the magnetic photocatalytic particles could migrate at a greater rate to the surface of the membrane. Through performance tests of the PVDF modified membranes, it was found that a magnetic coagulation bath could promote more Fe3O4@TiO2 to aggregate on the surface of the membrane, which led to the blend membrane formed under the magnetic coagulation bath had better antifouling performance against humic acid solution under ultraviolet light irradiation. Membranes with 0.5wt% magnetic photocatalytic particles in a magnetic field coagulation bath performed best. When filtered under the condition of ultraviolet light, its pure water flux was 1752L/(m2h), and the rejection rate of 20mg/L humic acid solution was 67.17%. The flux attenuation before and after filtration was 38.84%, the flux recovery rate was 91.10%, and the irreversible pollution index was only 8.90%.

In-situ growing of metal-organic frameworks on three-dimensional iron network as an efficient adsorbent for antibiotics removal

Abstract Considering the low recyclability of powder adsorbents, an efficient method is needed to fabricate a novel three-dimensional (3D) adsorbents. Take advantage of the 3D iron network and admirable adsorption performance of the Fe-based metal-organic framework (Fe-MOF), a solvothermal method was used to in-situ growing a series of Fe-based MOFs (MIL-53(Fe) MIL-100(Fe) and MIL-101(Fe)) onto the iron network (MIL stands for Materials of Institute Lavoisier). The successful growing of MILs(Fe) on the iron network was verified by optical microscopy, SEM, XRD, FT-IR and XPS characterizations. As expected, the 3D MILs(Fe) (Fe/MILs) inherited the high adsorption capacity of powdery MILs(Fe), while excellent recycling performance was obtained. Among them, Fe/MIL-100(Fe) exhibited the highest performance towards tetracycline (TC), more than 95% of TC could be removed at fifth adsorption cycle. Mechanism indicated that the π-π and hydrogen bonding (H-bonding) interactions between Fe/MIL-100(Fe) and TC molecules played an essential role in the adsorption process. Besides, the Fe/MIL-100(Fe) adsorbent was stable in water with negligible iron leaching in solution. It is worth noting that Fe/MIL-100(Fe) kept a high adsorption performance towards TC in a wide pH range of 2–10 and suffered minor influence from the anion and humic acid in solution. Even in actual aqueous solution (tap water, river water and pharmaceutical wastewater), high performance was presented by the Fe/MIL-100(Fe) adsorbent. This work provided a new method to synthesis 3D MILs(Fe) adsorbents for wastewater remediation.

Development of highly permeable and antifouling ultrafiltration membranes based on the synergistic effect of carboxylated polysulfone and bio-inspired co-deposition modified hydroxyapatite nanotubes

Hybridization has become a powerful toolbox for developing ultrafiltration membranes with superior properties. However, it remains challenging to give full play to the utility of nanofillers because of poor bonding strength between polymers and inorganic nanomaterials. Herein, hydroxyapatite nanotubes (HANTs) were modified via bio-inspired polydopamine (PDA) and polyethylenimine (PEI) co-deposition. Meanwhile, polysulfone with carboxylation degree of 30% (PSF-COOH-30%) was synthesized by nucleophilic substitution reaction and employed as the membrane matrix. The results showed that when 0.3 wt% HANTs@PDA/PEI was incorporated, the pure water flux of the hybrid membrane achieved about 3.2 times that of the unfilled membrane and the rejection rate of bovine serum albumin (BSA) and humic acid (HA) remained 94.5% and 97.8%, respectively. Meanwhile, the flux recovery ratio for BSA and HA solutions (1 g/L) reached 90.8% and 93.7%, respectively. Specifically, the superiority of UF performance benefited from the synergistic effect of both the carboxylated polymer and the nanofiller. On one hand, the incorporation of HANTs@PDA/PEI promoted the formation of more porous membrane structure and improved the hydrophilicity of the membrane. On the other hand, due to the existence of COOH, the electrostatic repulsion between the membranes and contaminants enhanced the fouling resistance for BSA and HA. Conspicuously, the ease and versatility of co-deposition provide new ideas in the construction of nanohybrid and the favorable improvement renders that appropriate combination of polymer and additive is an effective way for developing future ultrafiltration membranes.

Striking analogies and dissimilarities between graphene oxides and humic acids: pH-dependent charging and colloidal stability

This study provides a comparative framework on the elucidation of analogies and differences in the interfacial protolytic processes and the associated colloidal behaviour of a typical humic acid (HA) and a set of single-layer graphene oxide (SLGO) and (multi-layered) graphite oxide samples in aqueous electrolyte media. The pH dependence of the surface charge densities of HA and SLGO was explored at three different salt concentrations by potentiometric acid-base titration, along with simultaneous determination of zeta potential and hydrodynamic sizes. Charging curves obtained in the pH range of 3 to 10 by cyclic titrations reveal the presence of a small hysteresis, proving the chemical stability of SLGO and graphite oxides in weakly acidic and alkaline solutions. HA and SLGO display a parallel shift of the pH-dependencies of their negative charge densities with increasing ionic strength, demonstrating a unique combination of particle and polyelectrolyte-like behaviour, which is absent for multi-layered graphite oxide exhibiting charging curves that resemble to “classical” colloidal particles. An accurate purification of SLGO results in inherent change in its surface properties; however, the salt tolerance of aqueous HA solutions is still superior to that of SLGO dispersions.

Light conducting photocatalytic membrane for chemical-free fouling control in water treatment

This work shows for the first time the convenient in-situ UV illumination of a titanium dioxide (TiO2) photocatalytic membrane via a sintered porous glass substrate for effective fouling reduction during water treatment. By directing light through the light conducting glass substrate, this concept overcomes the current challenge of photocatalytic membranes that direct light through turbid, light obstructing feed waters. Fouling was tested by filtering model solutions of humic acid (HA), bovine serum albumin (BSA) or sodium alginate (SA). Photocatalysis initiated by simply directing light via the permeate side through the porous glass substrate led to significant reductions in trans-membrane pressure (TMP) rise rates between backwashes and all model organic fouling compounds. Specifically, the UV-light exposed membranes showed a 3.0-fold and 2.4-fold reduction in total filtration resistance for BSA and SA solutions, respectively, which also showed 2.7-fold and 4.2-fold reductions in the irreversible fouling indices. Analysis by SEM coupled with fouling modelling showed the beneficial anti-fouling effects stemmed from reduced intrusion of organic material inside the TiO2 membrane pores, as well as reduced cake layer resistance. The novel, convenient light conducting photocatalytic membranes concept could be used for sustainable, low-chemical membrane filtration of polluted water.

Magnetic field assisted arrangement of photocatalytic TiO2 particles on membrane surface to enhance membrane antifouling performance for water treatment

Fabrication of membranes with high antifouling and self-cleaning ability is a long-term pursuit of research community. For this purpose, the current work proposed a strategy to use an external magnetic field to arrange the magnetic TiO2@Ni particles (MNPs) onto the polymeric polyether sulfone (PES) membrane surface. The characterization results clearly indicated that the MNPs were successfully embedded onto the membrane surface instead of uniformly distributing into the membrane bulk. Because of this superficial distribution, the prepared composite membrane exhibited a flux of 871.2 ± 2.9 L·m−2·h−1·bar−1, which was 5 times flux of the pristine PES membrane. Meanwhile, it remained a rejection of 95.85% bovine serum albumin (BSA), which was also better than that of the pristine PES membrane. The cycle filtration experiments verified that the composite membrane possessed promoted antifouling ability for filtrating BSA, yeast extract fermentation (YEF), ammonium alginate (SA) and humic acid (HA) solutions. The antifouling mechanism was analyzed by the total interaction energies (ΔGTotal), which were quantitatively evaluated by using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. Moreover, it was interestingly found that the composite membrane possessed a self-cleaning property under radiation of UV light and sunlight. The optimal membrane after self-cleaning presented flux recovery ratio (FRR) of 75.4%, 99.56%, 92.11% and 98.26% for BSA, YEF, SA and HA solutions, respectively. This work demonstrated a novel way to fabricate membranes with high antifouling and self-cleaning ability for water treatment.

Preparation and antifouling performance of PVDF-DCOIT composite hollow fiber membranes

Membrane fouling is the main bottleneck that hinders the applications of membrane bioreactors (MBRs). 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), as an environmentally-acceptable antifouling biocide, was mixed with Polyvinylidene fluoride (PVDF) to fabricate hollow fiber membrane via non-solvent induced phase separation (NIPS), which was able to effectively improve the antifouling performance of the membranes in this work. Overall research of the prepared membrane revealed that membranes with 3 wt% DCOIT exhibited the optimum antifouling performance. With the addition of DCOIT, hydrophilicity and pure water flux of 3 wt% DCOIT membranes maintained remarkable improvement by 22.9% and 64.6% than that of membranes without DCOIT. Meanwhile, the surface morphologies of 3 wt% DCOIT membranes were smoother than the control group in terms of SEM and AFM images, which was beneficial to alleviate membrane fouling. In antifouling experiments, the flux variation rate of membranes with 3wt% DCOIT filtrated in bull serum albumin, sodium alginate and humic acid solution were 81.42%, 54.25%, 50.5%, while membrane without DCOIT were 64.6%, 24.72% and 29%, respectively. Similar results were obtained by filtrating anaerobic sludge for 24 h. The flux variations of 3 wt% DCOIT membranes were 59.4%, 47.8% and 46.0%, respectively in three stages. However, the flux variations of membranes without DCOIT were 44.8%, 36.7% and 19.8%, respectively, which showed better antifouling ability and higher flux recovery efficiency The novel membranes would provide some theoretical basis and technical support for the rational combinations in elevating the overall antifouling properties of membranes.