Empirical Relationship among the Parameters in HLD Equation of Block Polyether Water Clarifier.

In this work, the empirical relationship among three apparent parameters in the hydrophilic-lipophilic deviation (HLD) equation was studied to provide help in using the HLD equation to design a block polyether water clarifier for treating produced water in an oilfield. Ten block polyethers (including six linear polyethers and four branched polyethers) were prepared, and their HLD equations were measured. By curve fitting, the empirical relationship among apparent hydrophobicity characteristic (K), apparent characteristic curvature (Cc n ), and apparent temperature coefficient (c t) of block polyether were obtained: K = 9.32c t, Cc n = 18e-24.5K (for linear polyether), and Cc n = 3.7e-20.8K (for branched polyether). By introducing these relationships into the HLD equation and combining an empirical relationship between propylene oxide/ethylene oxide (mole ratio) in a block polyether and K/Ccn, a new block polyether was designed to treat the produced water. The treatment result confirmed the reliability of these empirical relationships. The results expand the practical application of HLD theory and are useful for the development of a block polyether water clarifier.

Effect of the Surfactant Type on the Demulsification of the W/O Crude Oil Emulsion Produced by Surfactant-Polymer Flooding.

At present, there are many works on the influences of partially hydrolyzed polyacrylamide (HPAM) and surfactant on the stability and treatment of O/W emulsion produced by surfactant-polymer (SP) flooding. However, there are few related reports on the effects of HPAM and surfactant on the demulsification of W/O crude oil emulsion produced by SP flooding. Especially, there is no report on the effect of the surfactant type. In this paper, sodium dodecyl sulfate (SDS), octylphenol polyoxyethylene ether (OP-10), and alkyl C16-18 hydroxypropyl sulfobetaine (HSB1618) were selected as representatives of the anionic surfactant, nonionic surfactant, and zwitterionic surfactant, respectively. Demulsification experiments and interface behavior experiments were conducted to investigate their influences on the demulsification performance of a demulsifier D1. The results showed that the order of the negative effect of the surfactant type on dehydration speed and the dehydration rate of D1 was HPAM + OP-10 > HPAM + HSB1618 > HPAM + SDS. There is no difference in the effect of three surfactants on the conformation adjustment of D1 at the W/O interface, but the properties of the composite W/O interface formed by them and D1 were different. The coalescence time was longest when there were HPAM and OP-10 in water, while the lg(G 1'/G demulsifier')/lgG 1' was the smallest, which led to the most difficult demulsification of W/O emulsion. This work can guide surfactant selection during SP flooding from the perspective of produced fluid treatment.

Study on the structure-activity relationship of cationic polyacrylates for the treatment of oilfield produced water.

Cationic polyacrylates exhibit both reverse demulsification and flotation performance, which can avoid incompatibility between the reverse demulsifier and flotation agent during treatment of produced water from offshore oilfields. In our previous work, the effect of the structure of the cationic unit on the reverse demulsification and flotation performance of cationic polyacrylates was studied. However, the structure-activity relationship of cationic polyacrylates has not been systematically studied. In this study, the relationships between the structure (acrylate type, tertiary amine type, mass ratio of acrylate to tertiary amine, and degree of cationicity), interfacial properties (surface tension, interfacial tension, zeta potential, interfacial elastic modulus, interaction force between oil droplets, and film drainage time of an oil-covered bubble), and reverse demulsification and flotation performance of cationic polyacrylates were investigated. A reduction in the elastic modulus of the oil-water interface was the key factor for good reverse demulsification performance, whereas a decrease in the film drainage time of an oil-covered bubble was the key factor for good flotation performance. Ethyl acrylate (EA) was superior to methyl acrylate (MA), and dimethylaminopropyl methacrylamide (DPM) was superior to dimethylaminoethyl methacrylate (DEM). Increases in the mass ratio of ethyl acrylate to dimethylaminopropyl methacrylamide and the degree of cationicity were beneficial for reducing the elastic modulus of the oil-water interface and the film drainage time of an oil-covered bubble. This is the first time that the structure-property-performance relationship of cationic polyacrylates has been systematically studied. A cationic polyacrylate that exhibited both good reverse demulsification performance and good flotation performance is recommended.

Insights into Zwitterionic Surfactant Interactions at the Oil-Water Interface by Interferometry Experiments and MDS Calculations.

In this work, the interaction performance of zwitterionic surfactant [dodecyl dimethyl sulfopropyl betaine (DSB-12) and hexadecyl dimethyl sulfopropyl betaine (DSB-16)] at the n-octadecane oil surface is investigated from experimental and simulation insights. For a macroscopic experiment, interfacial interferometry technology was developed for real-time monitor interaction performances and to obtain the quantitative interfacial thickness and mass results. The Langmuir model was characterized by thermodynamic analysis, deducing the aggregation spontaneity of DSB-16 > DSB-12 with ΔGagg(DSB-16) = -5.94 kJ mol-1 < ΔGagg(DSB-12) = 24.08 kJ mol-1. A three-step dynamic model (adsorption, arrangement, and aggregation) was characterized by kinetic analysis, indicating arrangement process as slow-limiting step with k2(arr) < k1(ads), k3(agg). For microscopic simulation, and molecular dynamic (MD) method was utilized to theoretically investigate interaction performances and obtain the interfacial configuration and energy results. The interaction stability and interaction strength were indicated to be DSB-16 > DSB-12 with differences of final energy ΔEfin = 48-88 kcal mol-1. The interaction mechanism was explained by proposing the model of "response enhancement" and "deposition activity" for DSB-16 interactions, and "response decrease" and "elution activity" for DSB-12 interactions. The different performances can be attributed to the different interaction forms and forces of surfactants. This work provided a platform for performance and mechanism investigation between the surfactant molecule and oil surface, which is of great significance in reservoir exploitation and enhanced oil recovery (EOR).

Treatment of oil-based drilling cuttings by floatation-advanced oxidation two-step process.

In this paper, a floatation-advanced oxidation two-step process was proposed for deep oil removal of oil-based drilling cuttings (OBDC). In the first stage, a novel and simple degreasing solution was prepared and most of the base oil contained by OBDC was removed by flotation; in the second stage, the oil content of OBDC was further reduced by combined ultrasound + ozone (US + O3) advanced oxidation. The recommended degreasing solution was a mixture of methanol, ammonium chloride, and water with a mass ratio of 1.48.1 : 0.25. The best flotation process was as follows: a mass ratio of OBDC to degreasing solution of 1 : 10, stirring speed of 400 rpm and N2 flotation with a flow rate of 400 mL min-1 for 60 min. The oil content of OBDC can be reduced from 14.57% to 1.42% after flotation treatment and the degreasing solution can be reused more than five times. The optimal process of US + O3 advanced oxidation was as follows: a mass ratio of OBDC to water of 1 : 10, ultrasonic power of 1000 W, and an ozone flow rate of 4.0 L min-1 for 100 min. The oil content of OBDC can be reduced from 1.42% to 0.14% after US + O3 treatment at room temperature. The results of this paper provide a new method and idea for OBDC treatment.

Ultrasonication-flotation-advanced oxidation tertiary treatment of oil-based drilling cuttings.

The treatment of oil-based drilling cuttings (OBDCs) with high oil content is difficult. In this study, a tertiary treatment of ultrasonication-flotation-advanced oxidation for treating OBDCs with a high oil content of 20.10 wt% was proposed for the first time. All stages of the treatment processes were optimised. The recommended parameters for ultrasonication at room temperature were a mass ratio of OBDCs to the degreaser of 1:8, an ultrasonication power of 600 W and treatment time of 30 min. After the ultrasonication treatment, the oil content of the OBDCs decreased from 20.10 wt% to 5.00 wt%. Flotation was performed at room temperature with a mass ratio of OBDCs to the degreaser of 1:10, a stirring speed of 400 rpm, an aeration head aperture of 3 µm and airflow rate of 400 mL/min under N2 injection for 60 min. After the flotation treatment, the oil content of the OBDCs decreased from 5.00 wt% to 2.01 wt%. Advanced oxidation was performed at room temperature with a mass ratio of OBDCs to water of 1:10, 3.57 wt% sodium persulphate in water, 4.17 wt% ferrous sulphate heptahydrate in water and ultrasonication power of 1000 W for 100 min. Following the advanced oxidation treatment, the oil content of the OBDCs decreased from 2.01 wt% to 0.58 wt%. The results of this study provide a new method and idea for treating OBDCs with high oil content.

Investigation of Oil-Water Separation on an F-SiO2/TiO2-Based Superhydrophobic/Superoleophilic Surface: Experiment Evaluation and MD Simulation.

Experiment evaluation and mechanism analysis of separation performance are crucial for oily wastewater treatment. In this work, a fluorinated superhydrophobic/superoleophilic (F-SHPB/SOPL) surface was fabricated on a steel mesh substrate by double depositions of SiO2-TiO2 nanoparticles for high-roughness improvement and composite modification of fluorine-alkyl groups for low-energy achievement. Measurements of SEM, XPS, FTIR, laser scanning confocal microscope (LSCM), and excitation-emission matrix (EEM) were carried out for surface property characterization. The oil-water separation performances at the prepared F-SHPB/SOPL surface were investigated from experimental and simulation aspects. Separation tests, flux tests, and anti-contamination tests were performed by experimental methods. The results indicated that the surface showed excellent separation efficiencies (>99.2%) for oil-water mixture and oil-in-water emulsion, high permeate flux (>3000 L·m-2·h-1) for organic oils, and perfect anti-pollution/self-cleaning capacity for liquid and solid contaminations. The interaction energies and interaction distances were measured by ab initio molecular dynamics simulation (AIMD) simulations. With lower interaction energy (Eoil = -456.52∼-1044.22 eV) than that of water molecules (Ewater = -172.73 eV) and shorter distance (Doil = 4.42∼5.13 Å) than that of water molecules (Dwater = 11.49 Å), oil molecules showed higher interaction stability than water molecules on the F-SHPB/SOPL surface. The calculation revealed the essence of the oil-water separation phenomenon. This work not only proposes the fabrication methodology of the SHPB/SOPL material but also elucidates the intermolecular interaction for oil-water separation. The results can provide a fundamental basis for separation operation and removal treatment in industrial and domestic applications.

Liquid Metal-Tailored PEDOT:PSS for Noncontact Flexible Electronics with High Spatial Resolution.

Electric field-based noncontact flexible electronics (EF-NFEs) allow people to communicate with intelligent devices through noncontact human-machine interactions, but current EF-NFEs with limited detections (usually <20 cm) distance often lack a high spatial resolution. Here, we report a versatile material for preparing EF-NFE devices with a high spatial resolution to realize everyday human activity detection. Eutectic gallium-indium alloy (EGaIn) was introduced into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) chains to fabricate this material, named Ga-PP. The introduction of EGaIn successfully regulates the intra- and interchain interactions of PEDOT chains and thus increases the π-electron accumulation on Ga-PP chains, which facilitates improvement of the electron storage of Ga-PP and its noncontact sensing ability. The water solubility of the obtained Ga-PP can reach approximately 15 mg/mL, comparable to that of commercial PEDOT:PSS, thus making Ga-PP suitable for various design strategies to prepare EF-NFE devices. We demonstrate that a conductive textile with a noncontact sensing ability can be achieved by immersing a commercial silk fabric into a Ga-PP solution for 5 min. With a detection distance exceeding 1 m, the prepared Ga-PP-based conductive textile (Ga-PP-CT) possesses outstanding noncontact sensing sensitivity, showing advantages in tracing the locations of signal sources and distinguishing motion states. Surprisingly, even when placed in water, Ga-PP-CT can be used to monitor the movement signals of athletes in different sporting events and output specific noncontact response signals for different sports. Intriguingly, the Ga-PP solution itself can be used to construct noncontact sensing conductive circuits, displaying the potential to be incorporated into smart electronics.

N-methylene phosphonic chitosan aerogels for efficient capture of Cu2+ and Pb2+ from aqueous environment.

In this paper, N-methylene phosphonic acid chitosan (NPCS-PEI) was synthesized from chitosan, phosphorous acid, formaldehyde and hyperbranched polyethyleneimine (PEI), and Cu2+ and Pb2+ removal performance was examined in aqueous solution. NPCS-PEI exhibited three-dimensional porous architectures, with a specific surface area of 490.61 m2/g. The effects of pH, initial concentration, adsorption time, temperature and ionic strength on the adsorption capacity were investigated. The adsorption kinetics indicated that Cu2+ and Pb2+ adsorption onto NPCS-PEI follows a pseudo-second-order model. The adsorption isotherms agree well with the Langmuir isotherm model, and the maximum adsorption capacities of Cu2+ and Pb2+ on the NPCS-PEI are approximately 276.12 and 645.16 mg/g, respectively. The adsorption efficiency of NPCS-PEI remained above 85% after 5 adsorption-desorption successive cycles. Moreover, the NPCS-PEI aerogels had selective adsorption toward Cu2+. The FTIR and XPS analysis proved that amino, hydroxyl, and phosphonic acid groups were involved in the chelation with metal ions.

Insight into Organic Pollutant Adsorption Characteristics on a g-C3N4 Surface by Attenuated Total Reflection Spectroscopy and Molecular Dynamics Simulation.

Herein the adsorption characteristics of zwitterionic dye pollutant Rhodamine B (Rh+B-) on a g-C3N4 surface were investigated by both an attenuated total reflection spectroscopy (ATRS) experiment and a molecular dynamics simulation (MDS). For experimental investigation, g-C3N4 was coated on a silica optical fiber (SOF) surface to fabricate an adsorption film. According to the ATRS response, adsorption thermodynamics and thermodynamics results were in situ obtained and evaluated. The isothermal Langmuir model was used to calculate the adsorption equilibrium constants (Kads) and adsorption energies (ΔGads) for Rh+B- as 27.25 × 104 M-1 and -31.01 kJ mol-1, respectively, which indicated the spontaneous adsorption behavior of Rh+B- at the g-C3N4 surface. Using dynamic Elovich modeling, the rate constants of Rh+B- were found to be k1 = 0.0063 min-1 and k2 = 0.0004 min-1, which indicated two-stage adsorption at the g-C3N4 surface. For theoretical simulation, adsorption configurations and adsorption energies were systematically calculated by a molecular dynamics simulation (MDS) . Rh+B- molecules were inclined to orient in a parallel position at the g-C3N4 surface during low concentration but a perpendicular position at the g-C3N4 surface during high concentration. Combined with experimental and calculation results, this work revealed the microscopic adsorption performance and elucidated the intermolecular interaction between localized interfaces of g-C3N4 and hazardous dye pollutant. We propose an adsorption model to explain the process of surface interaction, which is based on molecular orientation and a force-driven mechanism. Electrostatic attraction and π-π interaction dominated the adsorption interaction with an adsorption energy of ΔGlow(ads) = -38.96 kJ mol-1 for low Rh+B- concentration, and electrostatic attraction dominated the adsorption interaction with an adsorption energy of ΔGhigh(ads) = -25.76 kJ mol-1 for high Rh+B- concentration. This work can provide a fundamental basis for a dye-pollutants removal application by g-C3N4 in both adsorption and photocatalyzation.

In-situ investigation of dye pollutant adsorption performance on graphitic carbon nitride surface: ATR spectroscopy experiment and MD simulation insight.

The adsorption performances on graphitic carbon nitride (g-C3N4) surface were investigated for organic dye pollutants by both experimental and calculation methods. For experimental investigation, adsorption thermodynamics and kinetics results were in-situ obtained and evaluated. With [Formula: see text] by Langmuir modeling, g-C3N4 showed superior adsorption spontaneity of MB+ >MO-. With linear and exponential modeling, g-C3N4 showed only adsorption process for MB+ but both diffusion and adsorption processes for MO-. For simulation insight, all MB+ molecules but only parts of MO- molecules were inclined to orient in parallel position at g-C3N4 surface after optimization during low concentration. And both MB+ and MO- molecules were inclined to orient in perpendicular position at g-C3N4 surface after optimization during high concentration. Combined with experimental and calculation results, a molecular-orientation and force-dominance mechanism adsorption model are proposed to explain the surface interaction processes between dyes and g-C3N4. Electrostatic interaction and π-π stacking interaction were revealed to dominate for MB+ adsorption, and π-π stacking interaction and van der Waals force were revealed to dominate for MO- adsorption. This work obtained 'localized' interfacial information and elucidated in-situ intermolecular interactions at g-C3N4 interface, which can provide fundamental basis for operation removal of organic dye pollutants by g-C3N4.

Synthesis and flocculation of a novel flocculant for treating wastewater produced from polymer flooding.

Preparation of a flocculant which can have high-oil removal and no viscous flocs production for treating oily wastewater produced from polymer flooding (OWPF) is meaningful work. In this paper, a novel flocculant (denoted as PDC12DM) for treating OWPF was prepared by copolymerization of dodecyl dimethylallyl ammonium chloride (C12DM) and dimethyl aminopropyl methacryamide (DMAPMA). By using oil removal and viscous floc production as indexes, the synthesis condition of PDC12DM was optimized. The optimum PDC12DM had an oil removal of 98.8% and a viscous floc production decrease of 62.86% compared with commercial cationic flocculant. Measurement of zeta potential, surface tension, interfacial tension, interfacial film strength and dual polarization interferometry tests were carried out for investigating the flocculation mechanism of PDC12DM. The results showed that PDC12DM can destroy oil droplet stability by electrostatic charge neutralization and demulsification together. Especially, demulsification mechanism is helpful for reducing the viscous floc.

Application of choline-based deep eutectic solvent for the extraction of crude-oil contaminated soils.

Choline-based deep eutectic solvents (DESs) have many outstanding features as they are easy to prepare, inexpensive, low-toxic, low volatile, and biodegradable, which make them increasingly attractive in industrial chemistry and green chemistry. In this paper, the abilities of three different kinds of DESs for crude oil removal from contaminated soils were compared and it was found the DES formed by phenylpropionic acid and choline chloride (mole ratio = 2:1) had the best performance. The effects of extraction time, temperature and the solvent-soil ratio on phenylpropionic acid/choline chloride DES performance were evaluated. The rational extraction conditions were recommended as follows: mass ratio of DES to soil was 10:1 and 60 min extraction time at 80°C. The extraction (desorption) process could be described by Freundlich desorption isotherm mode. In addition, the phenylpropionic acid/choline chloride DES could be recycled and the oil removal efficiency was about 90% after 10 cycles. This finding suggested that choline-based DES extraction was a promising technology for crude oil removal from contaminated soil.

Preparation of poly-dopamine-silk fibroin sponge and its dye molecular adsorption.

This paper proposes a process for fabricating a poly-dopamine-silk fibroin sponge (PDA-SF) by using dopamine self-assembly and coating the skeleton of a silk fibroin sponge. The PDA-SF sponge was characterized by SEM, TEM, XPS, XRD and FT-IR. It was found that the sponge exhibits sheet structures with a pore size of 60 ± 20 µm and poly-dopamine adhered to the surface of pure silk fibroin through noncovalent bond forces. With a hierarchical porous structure, the derived sponge provides fast flow channels and abundant active sites, which will benefit the diffusion and removal of cationic dyes. Batch adsorption and dynamic adsorption of crystal violet (CV) were studied. The batch adsorption capacity of the PDA-SF sponge for CV increased with its PDA content. Under a dynamic adsorption mode, the adsorption efficiency of the PDA-SF sponge for CV (5 mg/L, 200 mL) can reach up to 98.2% after 12 min, whereas it is only 90.2% under stationary mode after 72 h. Furthermore, the sponge shows an outstanding smart adsorption performance. More importantly, the composite sponge still keeps high separation and adsorption efficiencies after 20 cycles, and the appearance remains good.

Investigation on the Adsorption-Interaction Mechanism of Pb(II) at Surface of Silk Fibroin Protein-Derived Hybrid Nanoflower Adsorbent.

For further the understanding of the adsorption mechanism of heavy metal ions on the surface of protein-inorganic hybrid nanoflowers, a novel protein-derived hybrid nanoflower was prepared to investigate the adsorption behavior and reveal the function of organic and inorganic parts on the surface of nanoflowers in the adsorption process in this study. Silk fibroin (SF)-derived and copper-based protein-inorganic hybrid nanoflowers of SF@Cu-NFs were prepared through self-assembly. The product was characterized and applied to adsorption of heavy metal ion of Pb(II). With Chinese peony flower-like morphology, the prepared SF@Cu-NFs showed ordered three-dimensional structure and exhibited excellent efficiency for Pb(II) removal. On one hand, the adsorption performance of SF@Cu-HNFs for Pb(II) removal was evaluated through systematical thermodynamic and adsorption kinetics investigation. The good fittings of Langmuir and pseudo-second-order models indicated the monolayer adsorption and high capacity of about 2000 mg g-1 of Pb(II) on SF@Cu-NFs. Meanwhile, the negative values of Δ r G m ( T ) θ and Δ r H m θ proved the spontaneous and exothermic process of Pb(II) adsorption. On the other hand, the adsorption mechanism of SF@Cu-HNFs for Pb(II) removal was revealed with respect to its individual organic and inorganic component. Organic SF protein was designated as responsible 'stamen' adsorption site for fast adsorption of Pb(II), which was originated from multiple coordinative interaction by numerous amide groups; inorganic Cu3(PO4)2 crystal was designated as responsible 'petal' adsorption site for slow adsorption of Pb(II), which was restricted from weak coordinative interaction by strong ion bond of Cu(II). With only about 10% weight content, SF protein was proven to play a key factor for SF@Cu-HNFs formation and have a significant effect on Pb(II) treatment. By fabricating SF@Cu-HNFs hybrid nanoflowers derived from SF protein, this work not only successfully provides insights on its adsorption performance and interaction mechanism for Pb(II) removal, but also provides a new idea for the preparation of adsorption materials for heavy metal ions in environmental sewage in the future.

Chemisorption mechanism of crude oil on soil surface.

One of the main challenges in cleaning crude oil-contaminated soil is the unknown adsorption mechanism between residual oil and soil. Herein, infrared spectrometer (IR) is used to detect the existence of dibutylphthalate (DBP) and pelargonamide on montmorillonite (MMT) surface. In addition, after the adsorption of DBP and pelargonamide on MMT, the bands in fingerprint region of the two IR spectra are almost identical, indicating coordination bonds were formed on the surface of MMT. X-ray photoelectron spectroscopy (XPS) is employed to detect the chemical environment of N, O and Al. The reverse migration of Al2p spectrum and forward migration of N1s and O1s spectra indicate the coordination adsorption of carbonyl and amine groups on MMT surface. Then, density functional theory (DFT) calculations are applied to make a further explanation of the bonding mechanisms of DBP and pelargonamide onto MMT surfaces. The result shows that there are two types of aluminum on the surface of MMT acting as Lewis acid sites in coordination adsorption, namely Al3+/Si4+ isomorphic substitutions and Al3+ adsorbed on MMT by means of electrostatic adsorption. Meanwhile, the oxygenium on the surface of MMT acts as Brønsted bases in hydrogen bonding adsorption.

Insight into the Synergistic Effect of Adsorption-Photocatalysis for the Removal of Organic Dye Pollutants by Cr-Doped ZnO.

The adsorption of dye molecules is an important process for the photodegradation removal of dye pollutants. In this work, a semiconductor photocatalyst of Cr-doped ZnO nanorods (Cr-ZnO NRs) was synthesized, and its adsorption-photocatalysis synergy (APS) effect was investigated for anionic methyl orange (MO-) and cationic methylene blue (MB+). The detailed thermodynamic information (including adsorption maximum capacity qmax, adsorption equilibrium constant Kads and adsorption efficiency AE %) and dynamic information (including adsorption rate constant ka, degradation rate constant kd and degradation efficiency DE %) were obtained to evaluate the different reaction performances for MO- and MB+. With qmax(MB+) = 40.59 mg g-1 > qmax(MO-) = 15.95 mg g-1, ka(MB+) = 20.61 min-1 > ka(MO-) = 4.62 min-1, and AE(MB+) = 40% > AE(MO-) = 9%, Cr-ZnO NRs showed much superior adsorption performance for MB+ than MO-. With kd (MB+) = 0.0430 min-1 > kd (MO-) = 0.0014 min-1 and DE(MB+) = 98% > AE(MO-) = 20%, Cr-ZnO NRs also showed much superior photodegradation performance for MB+ than MO-. The APS mechanism of Cr-ZnO NRs is revealed to be multiple π-π interactions and stronger electrostatic attractions dominant for enhanced adsorption of MB+ and higher AE and more photocatalytic active species dominant for enhanced photodegradation of MB+. The APS was furthermore characterized and verified by zeta potential analysis, Fourier transform infrared investigation, and fluorescence imaging. The results indicate that Cr-ZnO NRs are promising adsorbent and photocatalyst candidates favorable for positive MB+ than negative MO-. Such an APS investigation can effectively help to improve the photodegradation treatment performance of photocatalysts for dye pollutant removal.

In Situ Measurement of Depletion Caused by SDBS Micelles on the Surface of Silica Particles Using Optical Tweezers.

Dual-trap optical tweezers have been used to directly measure the interaction forces between two silica particles upon controlling the concentration of the ionic surfactant sodium dodecylbenzenesulfonate (SDBS). By capturing two silica particles in one spot optical trap and one linear optical trap and controlling the linear trap to bring one particle to approach another sufficiently closer, the interaction forces between these two particles can be measured as the separation distance changes. Results showed that with increasing concentrations of SDBS, the interaction force between the two silica particles emerges at closer surface distance between two silica particles. Only repulsive force exists between silica particles below the critical micelle concentration (cmc) of SDBS and it could be well-fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. However, the depletion attraction force appears above the cmc of SDBS which is induced by the generation of SDBS micelles. By in situ measurement of the interaction force between two silica particles in the presence of different concentrations of SDBS, the depletion force can be quantitatively calculated.

Insight into the Adsorption-Interaction Mechanism of Cr(VI) at the Silica Adsorbent Surface by Evanescent Wave Measurement.

The investigation of adsorption performance at the adsorbent surface can help to reveal the treatment mechanism and improve the treatment efficiency of adsorption technology for heavy metal ions (HMIs). This work developed a methodology to investigate the adsorption behavior of HMI Cr(VI) at the silica surface by confined near-field evanescent wave (CNFEW) measurement. A silica optical fiber (SOF) was used as the adsorption substrate and light waveguide element to integrate both Cr(VI) adsorption and CNFEW production on its surface. According to the sensitive CNFEW response, the adsorption behavior of Cr(VI) was in situ monitored and real-time evaluated. The thermodynamic information of adsorption equilibrium constant (Kads) and adsorption free energy (ΔG) and dynamic information of the apparent adsorption rate (vads) and adsorption time (tads) were obtained through Langmuir isotherm and kinetic fitting, respectively. Different reaction performances between Cr(VI) and adsorption sites were successfully differentiated, evaluated, and characterized. A site-decided-mechanism was therefore presented to describe the surface interaction process for Cr(VI), which including fast adsorption on type I Si-O- site through electrostatic attraction with [Formula: see text] and slow adsorption on type II Si-OH site through coordinative interaction with ΔGSiOH-Cr(VI)II = -26.18 kJ mol-1. The adsorption mechanism of Cr(VI) at the SOF silica surface was furthermore verified by zeta potential analysis, Fourier transform infrared investigation, and fluorescence imaging. Unlike conventional ex situ or in bulk detection, the present CNFEW-based approach targets the "localized" adsorption of Cr(VI) adsorbed to the solid adsorbent surface. Consequently, our work favorably constructs a surface platform and provides new insights on understanding the adsorption mechanism for HMIs.

Hydrazine-Functionalized guar-gum material capable of capturing heavy metal ions.

This research demonstrates the capability of guar-gum modified with salicylhydrazine to remove Ni2+, Co2+ and Cr3+ from aqueous solution. Structural characterization showed that aldehydes guar gum was grafted with salicylhydrazine with morphology. The as-prepared nanocomposite had a large surface area and hydrophobicity, which ensured its good sorption ability and convenience of separation. The sorption equilibrium data were well fitted to the Langmuir model, and uniquely high adsorption capacities for nickel, chromium and cobalt, which are 1272.4 mg•g-1, 748.86 mg•g-1 and 521.81 mg•g-1, remarkably, were achieved. The thermodynamic parameters for the sorption were also determined, and ΔG and ΔH values indicate exothermic behavior. Adsorption mechanism of capturing cation with GG-SH has been demonstrated through 1H NMR titration experiments of model molecular and metal ions. The features make this carbohydrate-based material suitable in water purification and separation treatment.