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•Acid surface dissolution converts some Fe2+ to Fe3+ ions on ilmenite surface.•Surface dissolution results in the formation of an insoluble hydrophobic layer of Fe(Ol)3.•Acid surface ...dissolution decreases the IEP of ilmenite and improves its floatability.
Acid surface dissolution as a pretreatment method converts Fe2+ ions on the ilmenite surface to Fe3+ ions. XPS analysis showed that the content of Fe3+ increases from 48.5% to 59.8% after surface dissolution for 15min in a solution of sulfuric acid with a concentration of 10%. This conversion, without any phase transformation, decreases the zeta potential of ilmenite in a wide pH range, resulting in a shift in IEP (Iso-Electric Point) from a pH of 5.4 to 2.3. FTIR spectra and zeta potential measurements showed that the increase of oleate ions adsorption on the ilmenite surface, resulting from the surface dissolution process, is insignificant. After surface dissolution, the formation of more ferric iron oleate species (Ksp=10−29.7) being more stable than ferrous iron oleate (Ksp=10−15.5) compounds yields an increase of ilmenite hydrophobicity and floatability in a wide pH range. Using 3.65×10−4M sodium oleate at a pH of 6.3, the maximum flotation recoveries are obtained as 73.5% and 92% for non-treated and acid pretreated ilmenite, respectively.
•Two-layered electroosmotic flow in the microfluidic channel is investigated.•Entropy generation analysis has been made to study Joule heating and MHD effects.•Thermal irreversibility of the system ...in terms of Bejan number is presented.•Joule heating effect causes enhancement of entropy generation.•The study has aim to design thermofluidic micropumps for mixing and separation process.
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We analyze the flow characteristics, thermal behavior, and entropy generation for two layered flow driven by combined effects of electroosmosis and peristaltic pumping in an asymmetric microfluidic channel subjected to velocity and thermal slip conditions. Aqueous solutions having different viscosity and different zeta potentials at the walls of the micro-channel are considered in upper and lower layers to examine the two layered flow variation. This study is motivated towards investigating micro-vascular two layered biofluid flow in capillary, by taking into account of heat transfer effects. Analysis is carried out under suitable physical assumptions (low Reynolds number, long wavelength and low zeta potential). The effects of slip parameter, viscosity, zeta potential and electroosmotic parameter on velocity field and the effects of Joule heating parameter, Brinkman number, thermal slip parameter on temperature field are reported. The variations in Nusselt number based on the velocity and temperature fields, and the variations in Bejan number based on heat transfer irreversibility are also computed. Furthermore, the implications of Joule heating on system irreversibility through entropy generation analysis due to fluid friction and heat transfer are studied. The outcomes of the present study is applicable in designing the thermofluidic micropumps which can be utilized in chemical mixing/separation processes and biomicrofluidics devices for the purpose of diagnosis.
Polycaprolactone based nanoparticles were prepared. Furthermore, in order to optimize the present formulation, process and formulation related parameters influence on obtained nanoparticles has been ...assessed and pointed out.
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•To obtain polymer based particles with suitable properties, formulation and operating conditions have been investigated.•Nanoprecipitation has been used as the method of particles preparation.•In formulation related parameters polymer concentration, and aqueous phase volume had a crucial impact on colloidal particles properties.•In operating conditions organic phase injection rate and agitation speed are the key factors to be taken into account.
Solvent displacement in comparison with other polymeric particles preparation technique provides certain crucial advantages such as water, time and energy lower consumption, procedure and set-up simplicity in nanoparticles preparation. The objective of this study was optimization of formulation in terms of the particle size, size distribution, zeta potential and morphology. In this study polycaprolactone based nanoparticles were prepared by solvent displacement or nanoprecipitation method. To prepare nanoparticles firstly, polycaprolactone was dissolved in acetone that form organic phase, secondly, for aqueous phase preparation, Tween® 80 and polyvinyl alcohol as stabilizer of the system, were dissolved in the water. Consecutively, under magnetic agitation organic phase was injected through a syringe to the aqueous phase. Acetone was removed under reduced pressure by rotavapor. Furthermore, different formulation and process related variables such as evaporation technique, organic phase injection method and rate, stabilizer nature, polymer concentration, Tween® 80 and polyvinyl alcohol concentration, stirring speed, organic and aqueous phases volume, were studied. To conclude, systematic study is indispensable before investigation of any drug encapsulation.
•Novel starch based nano-particles were used for encapsulating catechin.•Horse chestnut starch (HSC) had highest encapsulation efficiency and produced lower particle size.•Water chestnut starch (WSC) ...had highest stability and displayed slower release of catechin.•Nano-encapsulation helped in retaining bioactive properties of catechin during digestion process.
Novel starch-based nanoparticles from three sources: horse chestnut (HSC), water chestnut (WSC) and lotus stem (LSC) were prepared for nano-encapsulation of catechin. Average particle size of HSC, WSC and LSC based nano-particles were 322.7, 559.2 and 615.6 nm with encapsulation efficiency of 59.09, 48.30, and 55.00% and negative zeta potential of −18.05, −21.5 and −18.05 mv, respectively. Structural, physical and thermal properties were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). SEM revealed capsule formation with entrapped catechin, while broad characteristic peaks at 3475, 1650, 1383, 1148, 1083 and 790 cm−1 depicts encapsulation of catechin in starch nanoparticles without any evident interaction. XRD showed loss of crystallinity after encapsulation. Higher content of catechin in intestinal juice ensured controlled release in intestine. Bioactive properties were retained at higher level in encapsulated catechin compared to free catechin upon in-vitro digestion.
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•EDTA-mGO was synthesized firstly as a good adsorbent for Pb(II), Hg(II) and Cu(II).•Metal chelation and electrostatic attraction improved the adsorption ...capacity.•Pseudo-second-order, Freundlich and Temkin models analyzed the adsorption process.•Thermodynamics indicated the adsorption was an endothermic and spontaneous process.•EDTA-mGO could reproduce at least five recycles.
EDTA functionalized magnetic graphene oxide (EDTA-mGO), a good adsorbent for Pb(II), Hg(II) and Cu(II), was synthesized in the present work. It was characterized by SEM, FTIR, BET, XRD, XPS, TGA and zeta potential analysis. Contact time, adsorbent dose, pH and initial concentration were optimized to improve the removal efficiency. Most importantly, EDTA-mGO displayed better adsorption performance than EDTA-GO, EDTA-Fe3O4 and mGO. The adsorption of Pb(II), Hg(II) and Cu(II) mainly depend on the metal chelation of EDTA and the electrostatic attractions of abundant functional groups on GO surface. Besides, good magnetic performance of EDTA-mGO makes it easy to achieve the solid–liquid separation. The magnetic separation process only took 25s. The adsorption kinetic data described well with the pseudo-second-order model and the equilibrium data fitted well to Freundlich and Temkin isotherms. The maximum adsorption capacity was 508.4mgg−1 for Pb(II), 268.4mgg−1 for Hg(II) and 301.2mgg−1 for Cu(II) from Langmuir isotherm. Thermodynamic studies (ΔG<0, ΔH>0, ΔS>0) implied an endothermic and spontaneous adsorption process in nature. Furthermore, the excellent reproducibility indicated that EDTA-mGO has a promising application in water treatment.
Temperature gradient focusing (TGF) relies on establishing a precise balance between the electrophoretic motility of a target analyte and the advective flow of the background electrolyte (BGE) to ...locally concentrate the analyte in a microfluidic configuration. This paper presents a finite-element-based numerical analysis where the coupled electric field and the transport equations are solved to describe the effects of the shear-dependent apparent viscosity of a non-Newtonian BGE on the localized concentration buildup of a charged bio-sample inside a microchannel by TGF via Joule heating. Effects of the temperature-dependent nature of the wall zeta potential and the flow behavior index (n) of BGE on the flow, thermal, and species concentration profiles inside the microchannel have been investigated. Study using a fluorescein-Na analyte sample shows that the maximum normalized analyte concentration (C
/C
) reduces as the zeta potential increases linearly with temperature. The maximum concentration enhancement is achieved when the BGE displays the Newtonian rheology. For example, C
/C
increases 134- to 280-fold when n is increased from 0.8 to 1 (pseudoplastic regime) and again reduces to 190-fold when n increases further from 1 to 1.2 (dilatant regime).
Scheme of rational designed H+/GCL-chitosan for high nitrite adsorption capacity.
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•A feasible new strategy to enhance the nitrite adsorption of chitosan•Protonated imines are ...excellent anion adsorption sites•H+/GCL-chitosan has the highest nitrite adsorption capacity among chitosan adsorbents•Rapidly removing 95% of nitrite from high-concentration nitrite solution
Removing hazardous nitrite from water by chitosan has many advantages such as low cost, biocompatible, and abundant availability. However, its poor adsorption capacity for nitrite hinders its practical applications. More importantly, the strategies for improving the nitrite adsorption ability of chitosan are still elusive. In this work, a systematic strategy that considers adsorption sites, surface potential, and crystallinity was proposed to enhance the nitrite adsorption of chitosan. As a demonstration, a rationally designed amorphous adsorbent (H+/GCL-chitosan) with imine adsorption sites and positive surface Zeta potential was synthesized via heterogeneous cross-linking with glutaraldehyde and then acidified in HCl solution. The obtained adsorbent exhibited a high nitrite adsorption capacity of 17.30 mg·N·g−1, far surpassing the previously-reported chitosan-based adsorbents. Theoretical calculations and mechanism studies indicated that the designed imine adsorption sites and positive surface Zeta potential are crucial for its excellent adsorption capacity. Furthermore, H+/GCL-chitosan can rapidly reach adsorption equilibrium within 3 min and maintain stable adsorption for 24 h, and the adsorbent can be regenerated effectively. To demonstrate its applications, two H+/GCL-chitosan adsorption devices achieved over 95 % of nitrite removal rate with the initial nitrite concentrations of 10 and 100 mg·N·L−1 respectively, without any pretreatment of the polluted water. These results clearly show that H+/GCL-chitosan has an excellent ability for nitrite removal. Moreover, the surface engineering strategy proposed in this work may open up new possibilities for the efficient removal of nitrite from water using chitosan-based adsorbent.
ZIF-8 derived nanoporpous carbon (NPC) can be used as an efficient and recyclable adsorbent for the removal of ciprofloxacin, one of the most important emerging contaminants in water.
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...•Nanoporous carbon derived from MOFs was studied for the removal of CIP antibiotics.•Excellent CIP adsorption capacity of 416.7mg/g was obtained by NPC-700.•NPC-700 can be regenerated and reused for CIP removal, showing good recyclability.•Electrostatic and hydrophobic interactions played a key role in CIP adsorption.
The nanoporous carbons (NPC) derived from a one-step carbonization of zeolitic imidazolate framework-8 (ZIF-8) were synthesized and used for ciprofloxacin (CIP) removal from water. The resultant products were characterized by SEM, TEM, FT-IR, Raman, N2 adsorption-desorption analysis, XRD, TGA and Zeta potential. The optimized NPC-700 (carbonized at 700°C for 2h) exhibited an optimal performance in CIP adsorption removal. CIP adsorption on NPC-700 as a function of contact time, initial CIP concentration, adsorbent dosage, pH, ionic strength and humic acid concentration were investigated. Kinetics of CIP removal was found to follow pseudo-second-order rate equation. Both Langmuir and Freundlich models fitted the adsorption data well and gave similar correlation coefficients (>0.96). However, Freundlich isotherm gave a better fit (r2=0.9969), suggesting a multilayer adsorption of CIP onto surface of NPC-700 adsorbent. The maximum adsorption capacity for CIP based on Langmuir model was 416.7mg/g, which was higher than those of other adsorbents. The NPC-700 material showed no apparent loss in CIP adsorption after seven cycles. These features reveal that the metal-organic framework (MOF) derived NPC may be a promising adsorbent for CIP removal from water.
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