Eco-friendly calcium alginate microspheres enable enhanced profile control and oil displacement

Polymer microspheres(PMs),such as polyacrylamide,have been widely applied for enhanced oil recovery(EOR),yet with environmental concerns.Here,we report a microfluid displacement technology containing a bio-based eco-friendly material,i.e.,calcium alginate(CaAlg)microspheres for EOR.Two dominant mechanisms responsible for EOR over Ca Alg fluid have been verified,including the microscopic oil displacement efficacy augmented by regulating capillary force(determined by the joint action of interfacial tension and wettability between different phases)and macroscopic sweep volume increment through profile control and mobility ratio reduction.This comprehensive effectiveness can be further impacted when the CaAlg microsphere is embellished ulteriorly by using appropriate amount of sodium dodecyl sulfonate(SDS).The core flooding and nuclear magnetic resonance(NMR)tests demonstrate that CaAlg-SDS microsphere can balance the interphase property regulation(wettability alteration and IFT reduction)and rheology properties,enabling simultaneous profile control and oil displacement.Excessive introduction of SDS will have a negative impact on rheological properties,which is not favored for EOR.Our results show that the involvement of 4-m M SDS will provide the best behavior,with an EOR rate of 34.38%.This cost-effective and environmentally-friendly bio-microspherebased microfluidic displacement technology is expected to achieve“green”oil recovery in future oilfield exploitation.

Synthesis of phosphate-embedded calcium alginate beads for Pb(Ⅱ) and Cd(Ⅱ) sorption and immobilization in aqueous solutions

The phosphate-embedded calcium alginate beads were successfully synthesized based on sodium alginate, calcium dihydrogen phosphate and sodium hydrogen carbonate. Scanning electron microscopy, Fourier transformed infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were conducted to characterize the morphology and structure of the phosphate-embedded calcium alginate beads. The effects of pH and the initial concentration of the metal ions on Pb(II) and Cd(II) sorption by the beads were investigated. The optimal pH values for Pb(II) and Cd(II) sorption are 4.0 and 5.5, respectively. The optimal initial concentrations of Pb(II) and Cd(II) are 200 mg/L and 25 mg/L, correspondingly, and the removal efficiencies are 94.2% and 80%,respectively. The sorption mechanism is that the heavy metal ions accessed the beads firstly due to the large surface area, combinedwith OH?, and then precipitated with phosphate radical, which was proven by FTIR and XRD. The sorption of Pb(II) and Cd(II) isfitted to Langmuir isotherm model with R2 values of 0.9957 and 0.988, respectively. The sorption capacities of Pb(II) and Cd(II) are263.16 mg/g and 82.64 mg/g, respectively. The results indicate that the phosphate-embedded calcium alginate beads could be appliedto treating Pb(II)/Cd(II)-containing wastewater and it could be implied that the synthesized beads also could be used as a kind of soil ameliorant for remediation of the heavy metal contaminated paddy soil.

THERMAL DEGRADATION AND FLAME RETARDANCY OF CALCIUM ALGINATE FIBERS

Calcium alginate fibers were prepared by wet spinning of sodium alginate into a coagulating bath containing calcium chloride.The thermal degradation and flame retardancy of calcium alginate fibers were investigated with thermal gravimetry(TG),X-ray diffraction(XRD),limiting oxygen index(LOI) and cone calorimeter(CONE).The results show that calcium alginate fibers are inherently flame retardant with a LOI value of 34,and the heat release rate(HRR),total heat release(THR),CO and CO_2 concentrations during com...

CHEMICAL MODIFICATION OF THE SURFACE OF CALCIUM ALGINATE GEL BEADS

The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 °C for 30 min in 15 mL 1 % PVA/H2O. Then 4.34 moi/L VAc was added dropwise and the reaction was allowed to proce at 48 °C for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.

Removal and recovery of titanium(Ⅳ) from leach liquor of high-sulfur bauxite using calcium alginate microspheres impregnated with di-(2-ethylhexyl) phosphoric acid

In the leaching solution of high-sulfur bauxite roasted by sulfuric acid,a high concentration of aluminum presented along with titanium and iron.The present work was to remove Ti(IV)from the leach liquor by calcium alginate microsphere sorbent material(CA-P204)based on natural alginate impregnated with di-(2-ethylhexyl)phosphoric acid(D2EHPA)to purify leaching solution.Cation exchange and chelation make major contributions to the adsorption mechanism according to Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis.The results showed that Ti(IV)was successfully removed by the CA-P204 adsorbent from the Ti(IV)-Al(III)-Fe(III)ternary system with a dynamic column experiment.The removal rate of titanium was nearly 95%under optimal conditions and the maximum adsorption capacity was 66.79 mg/g at pH 1.0.Reusability of CA-P204 was evaluated over three consecutive adsorption/desorption cycles.The adsorption process was simple,low-cost,and had no waste discharge,suggesting that the CA-P204 was promising,efficient,and economical for removing Ti(IV)from high-sulfur bauxite leaching solution.

Recent advances in calcium alginate hydrogels encapsulating rejuvenator for asphalt self-healing

The inherent self-healing ability of asphalt is insufficient and fails to timely repair the cracks due to the combined effect of temperature variation,air oxidation,ultraviolet exposure and traffic loading.Rejuvenator encapsulation based on self-healing asphalt is a green sustainable preventive maintenance technology for asphalt pavement.During the last decade,rejuvenator encapsulation for asphalt self-healing has been a research hotspot and calcium alginate hydrogels encapsulating rejuvenator is a promising self-healing technology.Hence,this review sheds light on the recent advances of calcium alginate hydrogels encapsulating asphalt rejuvenator including selfhealing capsules and fibers.The synthesis methods of calcium alginate capsules and fibers containing rejuvenator were elaborately introduced,and their surface morphology,interior structure,mechanical strength,thermal stability,rejuvenator content,distribution and survival in asphalt materials were systematically analyzed.Besides,the effect of capsules and fiber on the mechanical property and pavement performance of asphalt concrete were explored.Additionally,a comprehensive review about the effect of calcium alginate capsules and fibers on selfhealing ability of asphalt materials were presented,and the rejuvenator release mechanism and release ratio of them in asphalt mixtures were expounded.In a nutshell,this review aims at highlighting the current research achievements on alginate capsules and fibers containing rejuvenator in asphalt materials,and inspiring enhanced self-healing methods for smart and sustainable maintenance of asphalt pavement.

Preparation and Characterization of Ferromagnetic Calcium Alginate Complex Gel

Fe3O4 suspension, derived from chemical coprecipitation and subsequent ultrasonic treatment, was embedded into calcium alginate to form complex gel. Both gel beads and injectable gel floc were obtained by slightly tailoring the preparation condition. SEM analysis showed that the iron oxide was dispersed homogenously in nanometer. TGA profiles revealed that the content of Fe3O4 in beads was about 7.2%.

Biodegradation of oil wastewater by free and immobilized Yarrowia lipolytica W29

The ability of Yarrowia lipolytica W29 immobilized by calcium alginate to degrade oil and chemical oxygen demand （COD） was examined. The degradation rules of oil and COD by immobilized cells with the cell density of 6.65 × 10^6 CFU/mL degraded 2000 mg/L oil and 2000 mg/L COD within 50 h at 30℃ （pH 7.0, 150 r/min）, similarly to those of free cells, and the degradation efficiencies of oil and COD by immobilized cells were above 80%, respectively. The factors affecting oil and COD degradation by immobilized cells were investigated, the results showed that immobilized cells had high thermostability compared to that of free cells, and substrate concentration significantly affected degrading ability of immobilized cells. Storage stability and reusability tests revealed that the oil degradation ability of immobilized cells was stable after storing at 4~C for 30 d and reuse for 12 times, respectively, the COD degradation rate of immobilized cells was also maintained 82% at the sixth cycle. These results suggested that immobilized Y lipolytica might be applicable to a wastewater treatment system for the removal of oil and COD.

Removal of copper ions from aqueous solution by calcium alginate immobilized kaolin

Kaolin has been widely used as an adsorbent to remove heavy metal ions from aqueous solutions. However, the lower heavy metal adsorption capacity of kaolin limits its practical application. A novel environmental friendly material, calcium alginate immobilized kaolin （kaolin/CA）, was prepared using a sol-gel method. The effects of contact time, pH, adsorbent dose, and temperature on Cu2＋ adsorption by kaolin/CA were investigated. The Langmuir isotherm was used to describe the experimental adsorption, the maximum Cu2＋ adsorption capacity of the kaolin/CA reached up to 53.63 mg/g. The thermodynamic studies showed that the adsorption reaction was a spontaneous and endothermic process.

Simple fabrication of Cu^(2+)doped calcium alginate hydrogel filtration membrane with excellent anti-fouling and antibacterial properties

Herein,copper ion doped calcium alginate(Cu^(2+)/CaAlg)composite hydrogel filtration membranes were prepared by using natural polymer sodium alginate(NaAlg)as raw material.The thermal stability and structure of the composite membranes were characterized by thermogravimetric analysis and infrared spectroscopy.The mechanical strength,anti-fouling performance,hydrophilicity and filtration performance of the membrane were studied.The results show that Cu^(2+)/CaAlg hydrogel membrane has excelle nt mechanical properties and thermal stability.The anti-swelling ability of the membrane was greatly enhanced by doping Cu^(2+).After three alternate filtration cycles,the flux recovery rate of Cu^(2+)/CaAlg hydrogel membrane can still reach 85%,indicating that the membrane has good antipollution performance.When the operation pressure was 0.1 MPa,the rejection of coomassie brilliant blue G250 reached 99.8%with a flux of 46.3 L m^(-2)h^(-1),while the Na_(2)SO_(4) rejection was less than 10.0%.The Cu^(2+)/CaAlg membrane was recycled after 24 h in the filtration process,and its flux and rejection rate did not decrease significantly,indicating that the hydrogel membrane has long-term application potential.The Cu^(2+)/CaAlg membrane has a wide range of applications prospect in dye desalination,fine separation and biopharmaceutical technology fields.

Cryopreservation of Cyrtopodium hatschbachii Pabst (Orchidaceae) immature seeds by encapsulation-dehydration

The aim of the present study was to investigate the efficiency of the encapsulation-dehydration technique for cryopreservation of Cyrtopodium hastchbachii Pabst seeds.Immature seeds of this species were cryopreserved by an encapsulation-dehydration technique.Seeds of five immature pods,120 days after pollination,were encapsulated in 3%calcium alginate matrix and pretreated in liquid medium supplemented with 0.08 M sucrose(24 h),0.15 M sucrose(24 h),0.25 M sucrose(48 h),0.5 M sucrose(24 h)and 0.75 M sucrose(24 h)in shaker at 60 rpm.Alginate beads were dehydrated 5 h in silicagel and immersed in liquid nitrogen for 12 h.Cryopreserved beads were thawed at 30℃ for 1 min,rehydrated using the same liquid mediums[0.75 M sucrose(24 h),0.5 M sucrose(24 h),0.25 M sucrose(48 h)and 0.15 M sucrose(24 h)]and cultivated in half strength Murashige&Skoog medium(1962)with the addition of 2 g/L activated charcoal.Sixty four percent of seeds survived and developed into acclimatized plants after being cryopreserved.In this work,the encapsulation-dehydration technique was employed for first time in Cyrtopodium hatschbachii.

Polypropylene non-woven supported fibronectin molecular imprinted calcium alginate/polyacrylamide hydrogel film for cell adhesion

Fibronectin （FN） imprinted polypropylene （PP） non-woven supported calcium alginate/polyacrylamide hydrogel film （PP-s-CA/PAM MIP） was prepared using non-woven PP fiber as matrix, FN as template molecule, sodium alginate （SA） and acrylamide （AM） as functional monomers, via UV radiation-reduced polymerization. The PP-s-CA[PAM MIP exhibited an obvious improvement in terms of adsorption capacity for FN compared with non-imprinted polymer （NIP）. The PP-s-CA/PAM MIP was successfully used for the culture of mouse fibroblast cells （L929） and the results showed that PP-s-CA]PAM MIP exhibited better cell adherence performance than the NIP did.

Enrichment of Cd^(2＋) from water with a calcium alginate hydrogel filtration membrane

A new method was developed for effective enrichment of Cd2+ ions from water with a calcium alginate(CaAlg) hydrogel filtration membrane. First, the CaAlg hydrogel filtration membrane was prepared without a pore-forming agent. This membrane was used to remove Cd^(2+) via ion exchange with Ca^(2+), and the Cd^(2+) was preserved in the CaAlg hydrogel. Then, the CaAlg hydrogel containing Cd^(2+) was soaked in a sodium citrate solution, and the hydrogel was fully dissolved. The removal rate of the CaAlg filtration membrane reached almost 100% within 120 min when the Cd^(2+) concentration was under 1 mg/L. Factors affecting the removal rate were investigated, such as NaAlg concentration, operating pressure, operating time and the initial concentration of Cd^(2+). The effects of initial Cd^(2+) concentration, pressure and filtration time on the enrichment factor were also investigated. The results show that the enrichment factor reached 87.3 when the pressure was 0.18 MPa and the filtration time was 240 min. Different enrichment factors could be achieved by adjusting the operating pressure and filtration time.

Transferring Process of RE^(3+) with the Microcapsules Containing P507

thylhexyl phosphonic acid mono-2-ethylhexyl ester (P507) was microencapsulated with ethyl cellulose and calcium alginate respectively.The microcapsules containing P507 can be used to extract and enrich Lu3+,Nd3+,and La3+ from aqueous solutions into them.Because of the immobility of the wall to the extractive agent,it changes the processes that the ions transfer into the agent (core material).Their relative transferring rates can be compared in accordance with permeative coefficiencies.The permeative coefficiencies will vary as the pH of the aqueous solutions is changed.Therefore,the differences of them between two ions can be enlarged in this way.The REP-507 complex can be stripped with 6 mol·L-1 HCl,which should enrich the ions quantitatively.

Evaluating the Efficiency of Cadmium Removal by Alginate Hydrogels from Water Using 5,7-Dibromo-8-hydroxyquinoline as a Complexing Reagent

Cadmium toxicity in wastewater is a rising concern due to industries like batteries,metallurgy,electroplating,plastic stabilizers,and pigments.The quantitative detection of Cd^(2+)and its remediation from wastewater samples are of major concern from an environmental point of view.In the present work,an effective spectrophotometric method has been reported using 5,7-dibromo-8-hydroxyquinoline(DBHQ)as a complexing agent for Cd^(2+).This method has advantages like using recyclable,less toxic solvents and easy sample preparation.The limit of detection,limit of quantification,and sensitivity of the proposed method were found to be 33.30,36.70 mg L^(−1),and 2×10^(−3),respectively.The DBHQ method was validated using atomic absorption spectroscopy,and the recovery percentage was more than 98%.These results indicate that DBHQ can be effectively used for monitoring Cd^(2+)in aqueous systems.The method developed was further employed for monitoring Cd^(2+)adsorption on calcium alginate(AL)hydrogels.Batch adsorption studies were done to optimize parameters of Cd^(2+)removal using AL hydrogels,and the data obtained were used for kinetic and thermodynamic studies.Kinetic studies indicated that the pseudo-first-order model showed better fitting,and thermodynamic studies showed Freundlich-like adsorption.The maximum adsorption capacity of Cd^(2+)on AL hydrogels was found to be 56.45 mg g^(−1).The validation studies of DBHQ were performed using statistical analysis methods like t-tests and one-way variance.

Photofermentative hydrogen production by immobilized Rhodopseudomonas sp. S16-VOGS3 cells in photobioreactors

One of the most important solutions to overcome energy and environmental problems and to replace the fossil fuel-based economy could be the use of photosynthetic microorganisms.The use of photosynthetic microorganisms is a potential alternative to energy generation from fossil fuels because they efficiently produce hydrogen(H_(2)).Immobilization of photosynthetic microorganisms is used for many biotechnological applications such as H_(2) production.This method appears attractive because it restricts cell movement in an entrapped matrix.Immobilization of Rhodopseudomonas sp.S16-VOGS3 cells is a promising way to improve H_(2) production.In this work,the ability of immobilized Rhodopseudomonas sp.S16-VOGS3 cells to produce H_(2) was investigated in two types of PBRs.The PBRs used in this work were a cylindrical one with 0.2 L working volume(C-PBR)and a flat Roux type with 0.6 L working volume(FRT-PBR).The calcium alginate beads prepared were resistant to culture mixing and showed little leakage of cells,and the immobilized cells continued the photofermentation process in both PBRs.The immobilized cells in the C-PBR produced 936.8 mL of H_(2) with an average H_(2) production rate of 2.99 mL/h.The average productivity was 126.4μL(H_(2))/mg(cells)/h or 14.96 mL(H_(2))/L(culture)/h,and the light conversion efficiency was 2.37%.The immobilized cells in the FRT-PBR produced a total of 662.2 mL of H_(2) with an average H_(2) production rate of 1.55 mL/h.The average productivity was 31.1μL(H_(2))/mg(cells)/h or 2.58 mL(H_(2))/L(culture)/h,and the light conversion efficiency was 0.52%.The more uniform and therefore more efficient degree of bacterial cell mixing achieved in the C-PBR with cylindrical configuration played an important role compared to the FRT-PBR.In the FRT-PBR,the beads were aggregated at the bottom,which limited light penetration and resulted in low H_(2) production efficiency.

The compartmented alginate fibres optimisation for bitumen rejuvenator encapsulation

This article presents development of a novel self-healing technology for asphalt pave- ments, where asphalt binder rejuvenator is encapsulated within the compartmented alginate fibres. The key objective of the study was to optimise the compartmented alginate fibre design, i.e., maximising amount of rejuvenator encapsulated within the fibre. The results demonstrate that optimum rejuvenator content in the alginate fibre is of 70：B0 rejuvenator/alginate ratio. The fibres are of sufficient thermal and mechanical strength to survive harsh asphalt mixing and compaction processes. Furthermore, results illustrate that zeer open asfalt beton （ZOAB） asphalt mix containing 5% of 70：30 rejuvenator/alginate ratio compartmented alginate fibres has higher strength, stiffness and better healing properties in comparison to the control asphalt mix, i.e., mix without fibres, and mix containing fibres with lower rejuvenator content. These results show that compartmented alginate fibres encapsulating bitumen rejuvenator present a promising new approach for the development of self-healing asphalt pavement systems.

A simple granulation technique for preparing high-porosity nano copper oxide(Ⅱ) catalyst beads

A simple and efficient method was developed for fabricating spherical granules of CuO catalyst via a three-step procedure. In the first step, copper oxide nanoparticles were synthesized by hydrothermal decomposition of copper nitrate solution under supercritical condition. Then, they were immobilized in the polymeric matrix of calcium alginate, and followed by high-temperature calcination in an air stream as the third step, in which carbonaceous materials were oxidized, to result in a pebble-type catalyst of high porosity. The produced CuO nanoparticles were characterized by transmission electron microscopy （TEM） that revealed an average size of 5 nm, X-ray diffractometry （XRD）, and thermo gravimetric （TG） analysis. The catalysts were further investigated by BET test for measurement of their surface area, and by temperature-programmed reduction analysis （H2-TPR） for determination of catalytic activity. The results demonstrated that immobilization of the CuO nanoparticle in the polymeric matrix of calcium alginate, followed by calcination at elevated temperatures, could result in notable mechanical strength and enhanced catalytic activity due to preservation of the high surface area, both valuable for practical applications.

Co-Free High-Entropy Alloys Powders Immobilized by Electrospray and Microf luidics for Decolorization of Azo Dye

In recent years,high-entropy alloys(HEAs)have received more and more attention due to their unique microstructure and properties.Several researchers have reported that some ball-milled(BM)HEAs powders possess prominent decolorization performance for azo dyes.Three kinds of Co-free HEA powders(AlCrFeMn,AlCrFeNi and FeCrNiMn)have been synthesized by ball milling in this work,of which AlCrFeMn shows the best decolorization efficiency for DB6 aqueous solution.However,at this time,the BM HEAs are in powder state and not easy to be reused,so the loss rate of the powders is high during the reaction.Sometimes,the reaction between reacted the powders and the dye solution is too fast to control.While,in order to solve these problems,this work proposes to immobilize bare BM AlCrFeMn HEA powders in calcium alginate beads(CAB s)by electrospray and microfluidics.Through four cycles of reaction,the loss rate of the AlCrFeMn powders can be reduced from 40 to 5 wt%if the powders are immobilized by CABs with an average diameter of 0.55 mm obtained at the DC voltage of 30 kV.In addition,in the four cycles of experiment,the AlCrFeMn HEA-CABs with an average diameter of0.55 mm shows better stability and easier separation than that of the bare AlCrFeMn powders.These findings provide new ideas for HEAs to decolorize azo dyes and are of great significance for protecting freshwater resources.