Colloids and Surfaces C: Environmental Aspects最新文献

Textile industry produces a great variety of effluents, rich in dyes, which have to be treated, in order to eliminate (or to decrease to secure levels) the contents of these environmentally harmful substances. The first step is the quantitative determination of dye concentrations in the effluent. In this manuscript, we propose a simple method to determine dye concentrations in solutions with two different dyes: acid blue 260, AB, and methyl orange, MO. It was demonstrated that correlating the apparent molar absorptivity of one of the dyes with the concentration of the other dye, a numerical method can be used to determine both dye concentrations and relative errors, using a single value of absorbance for each dye. The method was applied to the sorption of AB and MO on crosslinked chitosan, C-CHIT, and the more effective sorption of AB could be characterized by the determination of different isotherm parameters, estimation of Gibbs free energy of adsorption, as well as competitive sorption by itself.

To increase the collision probability between emulsified droplets and sponge surface for more efficient separation of emulsions, a durable superhydrophobic melamine sponge (MS) with nanoneedle-like surface was prepared through a simple and inexpensive route in this work. The fabrication processes included the formation of ZnO nanoneedles on MS surface via a hydrothermal method, followed by coating with polybenzoxazine based bisphenol A and dodecylamine (PB-D). As excepted, the resulting superhydrophobic sponge (PB-D/ZnO/MS) could effectively separate various surfactant-stabilized water-in-oil and oil-in-water emulsions, with a high permeation flux of up to 14,050 L m⁻² h⁻¹ and separation efficiency above 98.5 %, driven solely by gravity due to its nanoneedle-like surface. Moreover, PB-D/ZnO/MS also displayed outstanding absorption capacities for various oils and organic solvents (57.4–123.0 g/g) as well as prominent reusability, enduring 30 cycles of repeated absorption-squeezing without any evident decrease in water contact angle and absorption capacity (maintaining 90.9–96.6 % of initial value). In addition, the superhydrophobicity of PB-D/ZnO/MS remained almost unchanged after being immersed in strong acidic, alkaline and salty solutions for 48 h. Furthermore, PB-D/ZnO/MS not only showed outstanding flame retardancy but also remained rapid oil absorption rate under combustion conditions. Thus, the obtained superhydrophobic MS is a promising candidate for practical oil/water separation.

A kind of novel adsorbent, lanthanum carbonate modified microfibrous composite (LC-MC), is synthesized through a facile combined wet lay-up paper making and hydrothermal synthesis method. The fixed bed phosphate adsorption results show that LC-MC performs best when initial phosphate concentration is 5 mg/L, flow rate is 2.7 mL/min and bed height is 2 cm, with the maximum breakthrough time of 82.5 h and maximum adsorption capacity of 38.5 mg/g. High bed height and low flow rate are beneficial to the phosphate adsorption. Acid solution conditions benefit the adsorption process but will cause leakage of the lanthanum species (over 8 mg/L). 50 mg/L co-existing anions have no significant effect on the adsorption process, while concentrations more than 100 mg/L obviously inhibit the adsorption. The adsorbent also shows a good regenerability with less than 15 % decrease in adsorption capacity after 5 cycling runs. The adsorption kinetic process can be described better by the Yoon-Nelson model than Adams-Bohart model and Thomas model. Finally, the mechanism study indicates that the formation of phosphate lanthanum is the main reason for phosphate adsorption on LC-MC. Results show that LC-MC is a promising phosphate adsorbent to be used in fixed bed.

The effectiveness of High Gradient Magnetic Filtration (HGMF) in capturing uranium oxide particles from suspensions was investigated in this study. Two sets of experiments were performed to evaluate the importance of size on the capture of uranium oxide particles. The first considered two batches sieved into size bins of< 5, 5–10, 10–15, and 15–20 µm, while the second was performed using two suspensions with diameters smaller than 1.0 µm and between 1.0 and 1.5 µm. Iron oxide experiments, with particles between 0.3 and 0.8 µm, were performed for calibration purposes. In all experiments, a surfactant (Triton-X100 or sodium dodecyl sulfate) was used to prevent particle aggregation and limit the influence of non-magnetic capture mechanisms. A magnetic field of approximately 1.1 Tesla was generated using a water cooled electromagnet. HGMF was performed using tubular filters packed with ferromagnetic stainless-steel wool. Of the initial four uranium oxide particle sizes, magnetic capture was only observed for particles with a diameter of less than 5 µm, while larger particles experienced no magnetic and minimal total capture. For particles with diameters smaller than 1.0 µm and between 1.0 and 1.5 µm, capture efficiencies increased by 39 ± 9% and 34 ± 6% respectively, solely due to the magnetic field. Although the magnetic force is proportional to particle diameter, the capture efficiency decreased as diameter increased. These results suggest that Brownian diffusion, which is influential for micron sized particles and increases with decreasing particle size, is acting in conjunction with the magnetic force to influence the efficacy of HGMF for uranium oxide. This important finding underscores the effectiveness of Brownian diffusion in increasing the rate of collision between particles and collector fibers. A stochastic trajectory model was developed to incorporate the influence of Brownian motion on particle behavior and filter removal efficiency. Modeling results are discussed and compared for uranium and iron oxide particles.

Tetrahydrofuran (THF) and water are miscible and interact trough hydrogen (H) bonds. Span 80 (sorbitan ester) is soluble in THF, but not water. Nonetheless, Span 80 H bonds with water, as shown by attenuated total reflectance – Fourier transform infrared spectroscopy. In pure water, species are single (SD) or double (DD) donors, and single (SA) or double (DA) acceptors. In pure water, SD-SA and DD-DA are dominant and have similar abundance. Span 80 and THF alter the distribution of water species. When THF and Span 80 compete for the same water species, THF separation from water is most effective. Span 80 induces a marked shift of SD-SA to higher wavenumbers, which are close to DD-DA. This species intermediate between DD-DA and SD-SA is dominant, indicating that Span 80 mainly interacts with it. This same species is also dominant in THF-water mixtures containing 50–70% THF. Instead, DD-DA is dominant up to 40% THF, while DD-SA dominate at the highest THF percentages. Bottle tests show that Span 80 separates THF and water into bulk phases with 50–70% THF within 1 hr. In contrast, outside this THF range, emulsions are stable for more than 1 hr, as observed by either light scattering or optical microscopy. In mixtures with 50–70% THF, bulk phase separation occurs within 1 hr, because Span 80 competes with THF for the same water species. Separation is poorer outside of this THF range, where Span 80 and THF interact with different water species.

Superwettable coatings have aroused considerable attention in oil/water separation materials research benefit from their many advantages, such as various preparation methods, high separation efficiency, and low cost. However, many of these coatings are not suitable for practical separation due to the complex composite methods and poor biodegradability. The development of novel superwettable oil/water separation materials with simple fabrication and eco-friendly coating has become a noteworthy target in oil/water separation fields. Since the outbreak of COVID-19, a large number of waste masks abandoned in the natural environments have caused serious environmental hazards. The mask non-woven fabric (MNF) from waste disposable medical masks is a good separation material for its rich microporous. Herein, regenerated degreasing cotton cellulose and graphene oxide (GO) were used to successfully construct an environmentally friendly composite coating on the MNF through a simple dip coating method, and the obtained Cellulose/GO@MNF has excellent superhydrophilicity and underwater superoleophobicity. The fabricated coating possesses favorable chemical stability and nice mechanical strength after being destroyed by corrosive solutions (acid, alkali, salt solution) and physical processing (scratches). Various oil/water mixtures can be separated with high separation efficiency (>98%), and the separation efficiency is absent a substantive drop even after 10 separate cycles. Water can be removed quickly and continuously from the oil/water mixture by the as-fabricated MNF linking with a peristaltic pump. Besides, toluene oil-in-water emulsion can also be separated effectively. What is more significant is that, the Cellulose/GO@MNF fabric fabricated via a simple method and using biodegradable coating materials has potential application prospects in solving both recycling problems of waste masks and oil/water pollution.

An analytical expression is proposed to simulate effects of pH and redox potential (E) on the sorption of uranium onto bioorganic model particles in saline or other aquatic environments. The elaborated expression is intended to avoid use of the classical approach of sorption which relies on experimental data and empirical models. The goal is to produce an expression that provides a distribution coefficient (Kd e.g. mL g⁻¹) as function of pH, E and ligand concentration (through complex formation in solution) by applying a surface complexation model on one type of mono-dentate surface sites> (SuOH) as well as utilizing multi-dentate surface sites> (SuOH)_c. The formulation of the worked out expression makes use of correlations between the surface complexation and hydrolysis constants for all species and sorption sites. The model was applied to the sorption of uranium onto bioorganic sites with and without carbonates in solution e.g. Log Kd: + 2.75 at pH 8 for 2 sites per nm². The calculated distribution coefficients were found very sensitive to the presence of carbonates, e.g. Log Kd: − 7.0 at pH 8 for 2 × 10⁻³ M total carbonate. The potential reduction of uranium U(VI) and its complexes (carbonates) which are the primary stable species in surface waters, to U(IV) during sorption was simulated in association with a decrease in the redox potential and was found generally below the redox stability limits of water. The calculated distribution coefficient values were validated by the values reported in literature for the sorption of uranium onto specific adsorbents. The investigated simulations are also applicable to the sorption of other redox sensitive elements.

The wetting properties of droplets on microstructure surfaces directly determine the hydrophobic properties of the surface, and the size effect is an important part of the study of droplet wettability on microstructure surfaces. Taking reentrant special-shaped microstructure and doubly-reentrant special-shaped microstructure as the research objects, the influences of many geometric parameters of microstructure on the wetting characteristics of droplet with low surface tension were obtained by numerical simulation and theoretical analysis, and the concept of critical intrinsic contact angle was proposed. It is found that the two kinds of special-shaped microstructures can suspend the droplet with low surface tension, and the droplet finally presents a large apparent contact angle. However, there are three kinds of wetting transition (Cassie state →Wenzel state transition) on the surface of the doubly-reentrant special-shaped microstructure, so the wetting regulation mechanism of the surface with the same geometric parameters is different from that of the reentrant special-shaped microstructure. In addition, by analyzing the energy barrier at the pinning point, it is further proved that the doubly-reentrant special-shaped microstructure has better performance of inhibiting the wetting transition of droplet.