Use Of Adsorbents Research Articles

Enhanced adsorption and sensitivity for SF6 decomposition gas detection on penta PdSe2 monolayer: A Density Functional Theory investigation with van der Waals correction

The breakdown of the insulating gas SF6 causes the Gas-Insulated Switchgear (GIS) fault type to occur during high-voltage power operation putting the power system's safety in threat. The adsorption behaviour and sensitivity of five gases (H2S, SO2, SO2F2, SOF2 and HF) dissolved by SF6 on PdSe2 monolayers is explored using Density Functional Theory (DFT) in this work. Perdew-Burke-Ernzerhof (PBE) within a Generalised Gradient Approximation (GGA) was employed for the computational investigation. PdSe2 monolayer and SF6 decomposition gas adsorbed PdSe2 are built and optimized to get the most stable structures. The adsorption energy (Ead), charge transfer (QT), bandgap (Eg), Density of States (DOS), Work Function (WF), Sensitivity (S), and recovery time (τ) were computed to investigate the adsorption mechanism of PdSe2 monolayer to SF6 decomposition gas. The computation revealed that the SO2 and H2S adsorption systems have the highest adsorption energy of − 0.51 eV and − 0.52 eV respectively. The SO2F2 adsorption system has the weakest adsorption energy of − 0.44 eV. The findings show that PdSe2 systems have improved sensing performance for SO2 and H2S gas. The PdSe2 monolayer exhibits better sensitivity and a stable desorption time. The PdSe2 monolayer for SO2 and H2S detection shows high sensitivity, attaining 91.89% and 85.53%, respectively. This research establishes the groundwork for the development of PdSe2 monolayer adsorbents for use in SF6-insulated equipment.

Optimization of the Preparation Conditions of Aluminum-Impregnated Food Waste Biochar Using RSM with an MLP and Its Application in Phosphate Removal

Phosphorus is an essential macroelement in plant growth and the human body, but excessive water enrichment with phosphorus is a global threat to water quality. To address this problem, the development of an efficient, affordable adsorbent for use in removing large amounts of phosphorus from eutrophic water is necessary. Food-waste-based adsorbents offer a sustainable solution because they utilize waste as a valuable resource. This study explored the use of food waste biochar as a novel adsorbent with additional aluminum impregnation (Al–FWB) to enhance its phosphate adsorption capacity. This study employed response surface methodology (RSM) to optimize the synthetic conditions of the Al–FWB with the highest phosphate adsorption capacity. To enhance the identification of the optimal conditions using RSM, this study employed quadratic equations and a multi-layer perceptron (MLP). The pyrolysis temperature and Al concentration significantly (p < 0.05) affected the adsorption capacity of the AL–FWB. The optimal conditions for the preparation of the AL–FWB were a pyrolysis temperature, duration, and Al concentration of 300 °C, 0.5 h, and 6%, respectively, based on the quadratic equation and MLP models. X-ray photoelectron spectroscopy revealed that phosphate was adsorbed on the surface of the AL–FWB via the formation of AlPO4. The optimized AL–FWB (Opt-AL–FWB) removed 99.6% of the phosphate and displayed a maximum phosphate adsorption capacity of 197.8 mg/g, which is comparable to those reported in previous studies. Additionally, the phosphate adsorption capacity of the Opt-AL–FWB was independent of the pH of the solution, and the presence of 10 mM SO42– decreased its adsorption capacity by 15.5%. The use of the Opt-AL–FWB as an adsorbent provides not only efficient phosphate removal but also green, economical food waste reusability. In summary, this study demonstrates the potential of AL–FWB as an effective, sustainable, and affordable adsorbent for use in phosphate removal from contaminated water.

Optimization of Porous Phosphorylated Chestnut Starch Synthesis by Response Surface Methodology and Characterization of its Properties

AbstractPorous phosphorylated chestnut starch (P‐PCS) is prepared by enzymic hydrolysis of chestnut starch (CS) and phosphorylation, and the phosphorylation conditions are optimized by response surface design. The optimum reaction conditions are a compound phosphate (CP)/porous chestnut starch (P‐CS) mass ratio of 2:1, reaction temperature of 146 °C, and reaction time of 159 min. The degree of phosphate substitution of P‐PCS is 0.197. X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy demonstrate that phosphate groups are esterified with ‐OH groups on P‐CS. X‐ray diffraction (XRD) shows that the starch crystal form changes after both enzymatic hydrolysis and phosphorylation. Scanning electron microscopy (SEM) reveals that the surface of P‐CS is no longer as smooth as CS, but has different degrees of depressions and holes and P‐PCS grains are fractured and cracked. P‐PCS has much better light transmittance (26.4% vs. 2.6%) and Pb(II) adsorption performance (124.2 vs. 17.5 mg g−1) than CS, thereby providing a potential new application for chestnut starch as a natural polymer adsorbent for use in wastewater treatment.

Cellulose acetate-TiO2 and activated carbon electrospun composite fibre membranes for toluene removal

The VOCs removal from polluted air has been achieved using several different methods but primarily through the use of adsorbent materials or through degradation with photocatalytic oxidation (PCO). Fibres produced by electrospinning have the possibility to easily incorporate additives into the fibres and onto their surface. This can functionalise them for efficient VOCs removal. Cellulose acetate (CA)-based electrospun fibre membranes have been fabricated and doped with activated charcoal (AC) and titanium dioxide (TiO2), either separately or in combination to investigate their toluene removal capacity of the single additive and the synergic effects of adsorption and PCO. Two different methods of functionalisation of the fibres with AC and TiO2 have been used. These methods are air spraying and electro-spraying. Several configurations of the final membranes have been investigated. SEM images indicate that the additives have been successfully distributed on the fibre surface and they affect their morphology by increasing the overall roughness and the thickness of the final membranes. Adsorption with AC achieved 45.5% removal of toluene with a starting concentration of 22.5 ppm. PCO was probably initiated using a blacklight blue UV lamp with a peak wavelength of 365 nm as formation of formaldehyde was recorded. The findings suggest that PCO is affected by the residence time and UV light intensity.

Effect of sulfur dioxide on adsorption capacity of zeolite sorbents for carbon dioxide

The article discusses a rather serious problem limit-ing the use of adsorption for the CO2 capture from flue gas, in the presence of sulfur dioxide. An apparatus with a vertical batch adsorber was constructed to study adsorption under elevated pressure in a wide range of temperatures and evaluation of CO2 breakthrough curves with an infrared analyzer. The article summarizes the results of experiments conducted with zeolite clinoptilolite, which represented natural materials, and molecular sieve 13X as a representative of synthetic sorbents. Adsorption capacities achieved during cyclically repeated tests with a model gaseous mixture free of SO2 and a mixture of the same composition but enriched with a low volume fraction of SO2 (0.3 %) were compared. Adsorption took place at a temperature of 20 °C and at two overpressures (200 and 500 kPa) of the gas with a 13 % volume fraction of CO2. Each sub-experiment consisted of five adsorption and desorption cycles, where desorption was based on depressurization followed by temperature increase to 120 °C under nitrogen atmosphere. There were no changes in capacities when tested with the gaseous mixture without SO2. Relative to the weight of the sample, the 13X sample at an overpressure of 500 kPa had a capacity of 11.3 % and clinoptilolite 3.8 %. Tests in the presence of SO2 led to a permanent reduction of the equilibrium capacities for both samples and at both pressures. At the overpressure of 500 kPa, the capacity decreased to 7.4 % for the 13X and to 2.5 % for the clinoptilolite. A more intensive desorption involving a thermal and vacuum step did not lead to any improvement for the 13X sample. In contrast, the effect for clinoptilolite was very positive. Its capacity in the fifth cycle reached 3.4 % close to the state without SO2 exposition. In the case when SO2 in the gas was accompanied with 40 % relative humidity, vacuum desorption did not lead to positive results in any case. After five cycles, the capacity of 13X dropped to 3.2 % and clinoptilolite to 1.4 %. When moisture, SO2 and the presence of O2 (volume fraction of 6 %) in the model mixture were further combined, the capacity of 13X decreased to 1.4 % and clinoptilolite to 0.4 % after five cycles. Tests with SO2 (dry gas) caused a decrease in the specific surface area from 512 to 211 m2.g‒1 for the 13X sample. On the other hand, for clinoptilolite it decreased from only 29 to 28 m2.g‒1 under the same conditions. Ac-cording to XRF, it was not possible to remove sorbed SO2 from the 13X sample even by evacuation followed by heating up to 200 °C. Using the XRD method, it was found that SO2 remains in the matrix, although it does not undergo transition to the crystalline phase. The study verified that synthetic molecular sieve 13X, unlike natural clinoptilolite, is not applicable for CO2 adsorption from SO2 containing flue gas.

Adsorption of Pb(II) from Aqueous Solution Using Dendritic Fibrous Type SBA-15 (DFSBA-15)

The presence of heavy metals in the environment is undeniably harmful and toxic to living things, where the presence of Pb(II) inside human foods and drinks results in various diseases. The use of adsorption as a method of wastewater treatment is widespread, and effective adsorption performance depends on appropriate adsorbent selection. In this research, dendritic fibrous type SBA-15 (DFSBA-15) was prepared and used for lead (Pb(II)) adsorption. The physicochemical properties of the DFSBA-15 were characterized using TEM, BET, and FTIR. The characterization analyses confirmed the formation of fibrous morphology, moderate surface area, and bulk -OH. Several factors, including contact time (min), adsorbent dosage (g/L), pH, and initial concentration (mg/L), were examined for Pb(II) adsorption. The best adsorption performance (89.88%) was attained at 180 min, 1 g/L of adsorbent dosage, pH 5, and 100 mg/L of Pb(II) initial concentration. Pseudo-second-order reaction type and Langmuir isotherm provided good fits to the experimental data, with R2 ≥ 0.9943 and R2 = 0.9982, respectively. In short, the DFSBA-15 exhibits great potential for excellent Pb(II) removal.

Turbidity Reduction of Groundwater by Using Nanomagnetic Adsorbent Composite (NMAC): Process Optimization by 3k Factorial Design and Analysis

<p>The widespread use of alternative water sources in Kelantan encourages the development of cost-effective methods for the purification of water. A simple and straightforward adsorption process using a nanomagnetic adsorption composite (NMAC) was introduced in this study as a new adsorbent for the treatment of turbid polluted groundwater. The use of iron oxide nano-coated adsorbents (NMACs) showed a high porosity relative to commercial activated carbons (CACs). Analysis of X-ray diffraction analysis for NMAC is confirmed by a crystal framework for Fe2O3, Fe3O4, and FeO are cubic components. A 3k maximum factor configuration of four factors, i.e., adsorbent dosage (0.02, 0.04, and 0.06 g), agitation time (15, 30, and 60 min), rotation speed (150, 200, and 250 rpm) and adsorbent scale (< 45 μm and > 300 μm) were used. The turbidity removal capability of both NMAC and CAC was compared. The adequacy of the developed empirical model for the elimination of turbidity and maximum turbidity efficiency was determined by regression model analysis. The obtained results revealed regression values of NMAC (R2; 0.9903, R2 adj.; 0.9875, R2 pred; 0.9808) and CAC (R2; 0.9909, R2 adj.; 0.9981, R2 pred.; 0.9817). The analysis of variance and surface response methodology revealed that turbidity removal efficiency of NMAC is affected by the four factors investigated. Among the samples, 0.04 g NMAC (< 45 μm) agitated at 150 rpm for 48 min showed 98.76% maximum adsorption efficiency. The findings showed that NMAC is a strong adsorbent for use in the treatment of raw water.</p>

A new type of calcium-rich biochars derived from spent mushroom substrates and their efficient adsorption properties for cationic dyes.

Adsorption is commonly accepted as a most promising strategy in dye wastewater treatment, and the widespread use of adsorption emphasizes the need to explore low-cost but excellent adsorbents. Herein, a low-cost adsorbent (calcium-rich biochar) was developed, which was directly pyrolyzed from spent mushroom substate without any modification. This study evaluated the potential application of two calcium-rich biochars (GSBC and LSBC) derived from spent substrates of Ganoderma lucidum and Lentinus edodes, respectively. The effects of pyrolysis temperature on the calcium-rich biochars characteristics and their adsorption mechanism for cationic dyes (Malachite Green oxalate (MG) and Safranine T (ST)) were studied systematically. The increase in pyrolysis temperature from 350 to 750 °C led to an increase in both biochar ash, Ca content, and specific surface area, which made high-temperature biochars (GS750 and LS750) the superior adsorbents for cationic dyes. Batch adsorption results showed LS750 was more efficient to adsorb dyes than GS750 attributed to its higher Ca content and larger specific surface area. According to the Langmuir model, LS750 had high adsorption capacities of 9,388.04 and 3,871.48 mg g−1 for Malachite green and ST, respectively. The adsorption mechanism of dye MG could be attributed to pore filling, hydrogen bonding, electrostatic interaction, ion exchange, and π-π stacking, while ST adsorption mainly involved pore filling, electrostatic interaction, ion exchange, and π-π stacking. Attributed to their excellent adsorption performance, cheap source, and good reusability, biochars obtained from SMSs were very promising in dyeing wastewater treatment.

Reuse of aluminium-based water treatment sludge for phosphorus adsorption: Evaluating the factors affecting and correlation between adsorption and sludge properties

Equilibrium phosphorus (P) adsorption was investigated for nine aluminium-based water treatment sludges (WTS) from four water treatment plants in Victoria, Australia. Four WTS, one from each location, were characterised in-depth to unpack the P adsorption trends observed from the nine WTS. Morphology, surface area, porosity, mineralogy, and acid-digestible aluminium were measured. In a key finding resolving longstanding uncertainty on this topic, results indicate that the age of the sludge does not account for differences in P adsorption. However, there was a strong correlation between the acid-digestible Al content of the sludge, the surface area of the sludge and the P adsorption. Acid-digestible Al concentration may serve as a simple proxy to help identify WTS batches best suited to reuse for P adsorption. One of WTS was investigated in further detail to identify suitable conditions for use in adsorption. The highest P adsorption was observed at pH 4 (the lowest pH tested), with negligible release of Fe & Al at this pH. The second smallest fractions (1.18 mm) which showed the highest adsorption. We hypothesise that the smallest size fraction (0.6 mm) is composed of inert materials that do not participate in P adsorption. All WTS released organic content ranging from 1.63 mg/L to 9.7 mg/L into the solution in experiments and it was influenced by the pH and P concentration which supports that ligand exchange is the driving force. This study of provide useful information for water treatment plant operators to identify potential reuse applications for water treatment sludge. • Trends of P adsorption with WTS age do not correlate across multiple sites. • Acid digestible Al shows a strong correlation with surface area and P adsorption. • The particle size fraction less than 0.6 mm appears to be less active in P adsorption. • Organic release is influenced by pH and quantity of P adsorbed but not the sludge age.

Hydroxylation of UiO-66 Metal-Organic Frameworks for High Arsenic(III) Removal Efficiency.

Zirconium clusters of UiO-66 have been hydroxylated with NaOH to generate strong binding sites for As(III) species in wastewater treatment. Hydroxylated UiO-66 provides high adsorption capacity over a wide range of pH from 1 to 10 with a maximum uptake of 204 mg g-1, which is significantly enhanced compared to those of pristine UiO-66, acid-modulated UiO-66, and other adsorbents for use in a wide pH range of treatment processes. The local structure of hydroxylated sites and As(III) adsorption mechanism are determined by extended X-ray absorption fine structure combined with density functional theory calculations.

An Overview to Technical Solutions for Molybdenum Removal: Perspective from the Analysis of the Scientific Literature on Molybdenum and Drinking Water (1990–2019)

A bibliometric analysis using the Scopus database was performed to investigate the research documents published from 1990 to 2019 in scientific sources related to molybdenum in drinking water and determine the quantitative characteristics of the research in this period. The results from the analysis revealed that the number of publications was maintained at a regular production of around 5 papers per year until 2009, followed by a fast linear increase in the production in the period from 2010 to 2016 (29 papers in 2016), but the scientific production regarding this topic was reduced in 2017 and 2018 to recover the production obtained in 2016 once again in 2019. The total contribution of the three most productive countries (USA, China and India, respectively) accounted for around 50% of the total number of publications. Environmental Science was the most common subject (51.4% contribution), followed by Chemistry (26.7% contribution). The research efforts targeted toward the search for technical solutions for molybdenum removal from water are not as important as the ones focused on the identification of molybdenum-polluted water bodies and the analysis of the health effects of the intake of molybdenum. Nevertheless, examples of technological treatments to remove molybdenum from the aqueous solution include the use of adsorption and ion exchange; coagulation, flocculation and precipitation followed by filtration; membrane technologies and biological treatments.

Investigation of the elution behavior of dissociating itaconic acid on a hydrophobic polymeric adsorbent using in-line Raman spectroscopy

The use of adsorption for the purification of dicarboxylic acids is rather limited and currently predominantly confined to ion-exchange chromatography. A promising, but less regarded alternative is the use of hydrophobic adsorbents. Regarding hydrophobic absorbents, the literature focuses on screenings of adsorbents for purification of (di)carboxylic acids with regard to adsorption equilibria. The investigation of dynamic phenomena in the column received only minor attention. In this contribution, this knowledge gap is addressed. First, the adsorption behavior of itaconic acid species on the hydrophobic, highly-crosslinked polymeric adsorbent Chromalite™ PCG1200C is investigated. For this purpose, adsorption isotherms are determined via frontal analysis at pH values of 2, 3, 4.5, 6.5, and 8 to evaluate the dependency of the adsorption capacity on the dissociation state. Capacities above 150 g Lads−1 at liquid phase concentrations of 70 g L−1 are observed at a pH of 2. A strong decrease of capacity with increasing pH value, i.e., with increasing fraction of dissociated negatively charged acid species, is observed. Second, pulse experiments at aforementioned pH values are performed. Thereby, in-line Raman spectra are recorded at the column outlet, which allows the direct differentiation of the acid species state of dissociation. The spectral information is evaluated for quantitative concentration profiles of itaconic acid species using Indirect Hard Modeling with mixture hard models that are calibrated subject to ideal as well as non-ideal thermodynamics. In-line measurement errors of ≤ 3.5 g L−1 are achieved for the itaconic acid species. In dependency of the pH of the feed solution, a separation of the individual acid species within the pulse experiments is observed. It is conjectured that the process is dominated by a superposition of species-dependent adsorption characteristics and dissociation reactions.

Comparing the adsorption isotherms and kinetics of phosphate adsorption on various waste shells as adsorbent

Abstract Excess phosphate in water bodies causes algae bloom and this phenomenon can reduce the amount of dissolved oxygen in water bodies, resulting in the death of aquatic life. The major focus of this study is to prepare adsorbent from three waste shells for phosphate adsorption from aqueous solution and to compare their effectiveness. This study used adsorbents made from marsh clamshells, waste mussel shells, and eggshells. PO43– adsorption by these shells was analysed using several parameter values, with an initial PO43− concentration of 10 mg L−1, solution volume of 100 mL, adsorbent dosage of 2 g, and various contact times. The pseudo-second-order kinetic model fitted the batch experimental data better as evidenced by the R2 values for raw marsh clamshell (0.9991), calcined waste mussel shell (0.9999), and calcined eggshell (0.9997), indicating that the adsorption between the various adsorbents and PO43− is a chemisorption process. Calcined eggshell showed the best PO43− removal efficiency (99%), followed by calcined waste mussel shell (96%), and raw marsh clamshell (73%). The application of waste material to adsorb phosphate from aqueous solution shows the potential of a new adsorbents for use in real adsorption wastewater treatment technologies.

Functionalization of mesoporous carbons derived from pomelo peel as capacitive electrodes for preferential removal/recovery of copper and lead from contaminated water

• Waste pomelo peel converted into a novel adsorbent for use in CDI. • Removal of Pb and Cu ions strongly enhanced by functionalizing with pyrrolic-N. • Strong selectivity of Pb 2+ from water containing multiple competing ions. • Easy regeneration of adsorbent on no loss in performance over 300 cycles. Water is not only a valuable resource that is needed to sustain life, but also an essential ingredient in many engineering processes, which unavoidably leads to large volumes of water being contaminated. To achieve safe discharge and also recover valuable “pollutants”, better performing sorbents are needed to rapidly and efficiently decontaminate water while generating minimal secondary wastes. Bio-sorbents derived from pomelo peel were functionalized with pyrrolic-N (BNC-5 electrode) and pyridinic-N (BNC-6 electrode) to enhance electroadsorption and selectivity of Pb 2+ and Cu 2+ . The interaction between soft acid ions (Pb 2+ ) and soft base sites (pyrrolic-N) contributed to a strong chemisorption that elevated the electroadsorption capacity to 2.0 mmol g −1 for Pb 2+ at an applied voltage of 1.2 V. With fast removal kinetics (0.077 g mg −1 min −1 of Pb 2+ ), the BNC-5 sorbent performed comparably to other N-doped sorbents prepared using graphene. The large adsorption–desorption hysteresis of BNC-5 in responding to the applied electric voltage confirmed the nature of chemisorption. The results showed only 32.4% of the adsorbed ions being desorbed from the sorbent by reducing the applied voltage to 0 V, but reached almost complete desorption (98.5% of adsorbed ions) at –0.8 V. When operated in adsorption–desorption cycle mode, BNC-5 after ∼ 400 cycles maintained a capacity retention ≥ 80%. After 400 cycles, the electrode capacity was almost fully restored (98.7%) by only mild chemical washing (0.1 M HNO 3 ) of the sorbent and the cycling performance maintained. The study demonstrated the robustness of the sorbent over 1200 cycles and hence the potential to successfully convert waste into high-performance materials for large-scale remediation strategies of contaminated wastewater using CDI.

Ultrasound assisted synthesis of heterostructured TiO2/ZnFe2O4 and TiO2/ZnFe1.98La0.02O4 systems as tunable photocatalysts for efficient organic pollutants removal

As a response to the everyday growing concern about wastewater treatment, some new mesoporous TiO 2 /ZnFe 2 O 4 and TiO 2 /ZnFe 1.98 La 0.02 O 4 catalysts were synthesized during this research. The ultrasound template-assisted sol-gel method was employed in the synthesis, using conventional calcination and microwave treatment for pore directing agent removal. The as-prepared samples were characterized from the structural, optical, morphological and textural points of view, confirming the presence of spinel ferrites and TiO 2 anatase crystals in the nanocomposites. The synthetized powders exhibit promising characteristics for their use in adsorption and light activated degradation of organic pollutants. The photodegradation experiments of model pollutant basic blue 9 (methylene blue) dye were performed at laboratory scale and the optimum experimental parameters were determined as 0.4 g/L catalyst and 30 mg/L initial dye concentration, under UV light irradiation, visible irradiation and natural sun light irradiation. The conventionally calcined lanthanum doped TiO 2 /ZnFe 1.98 La 0.02 O 4 system exhibited the highest efficiencies of 97%, 70% and 91% for dye removal from the solution, under UV light, visible light and natural sun light irradiation, respectively. Moreover, the catalytic activity was similar for up to four consecutive cycles. A lower yield of organic pollutant removal was observed in wastewater treatment plant (WWTP) effluent. The obtained results show that the newly synthesized catalysts are good candidates for the removal of water pollutants through adsorption and photocatalysis.

Removal of Volatile Toluene Using K2CO3-Activated Carbon Adsorbents Prepared from Buckwheat Hull

Carbon adsorbents for use in the removal of gaseous toluene from the air were prepared from buckwheat (Fagopyrum esculentum Moench) hull. A chemically-activated adsorbent was prepared via the impregnation of raw hull powder with potassium carbonate, followed by thermal decomposition. The chemically-activated adsorbent exhibited improved adsorption capacity for toluene compared to the adsorbent prepared without chemical activation. Toluene concentration in the air decreased from 220 ppm to 160 ppm during 24 h of adsorption using unactivated adsorbent. Only a trace amount of toluene remained after the adsorption under the same conditions using K2CO3-activated adsorbent. This improvement was explained based on experimental results, specifically, iodine adsorption tests, methylene blue adsorption tests, and microscopic observations. Chemical activation dramatically increased the specific surface area of the adsorbent and created mesopores capable of adsorbing toluene. This study revealed that a mesoporous adsorbent for use in volatile toluene removal can be prepared from waste biomass (buckwheat hull) by chemical activation using potassium carbonate.

Synthesis of Cadmium(Ii)-Based Coordination Polymers and its Use for Adsorption of Diclofenac from Aqueous Solutions and Highly Sensitive Fluorescence Detection of Copper (Ii) and Nickel (Ii) Cations

Synthesis of Cadmium(Ii)-Based Coordination Polymers and its Use for Adsorption of Diclofenac from Aqueous Solutions and Highly Sensitive Fluorescence Detection of Copper (Ii) and Nickel (Ii) Cations

The cause of accelerated desorption of sparingly soluble dodecanol monolayers: Convection or leakage?

The dissolution of sparingly soluble surfactants from spread monolayers is a complex multi-staged process. The desorption of dodecanol from the surface of water follows mixed barrier/diffusion kinetics only in the first stages of the dissolution. Significant acceleration of the desorption has been observed experimentally after this initial period, which has been hypothesized to be due to onset of convective diffusion; the source of convection, however, has never been identified. The goal of this work is to investigate the question through desorption experiments under controlled convection and respective modeling of the process under mixed barrier/convective diffusion control. Several hypotheses for the cause of the accelerated desorption have been tested. The analysis has shown that natural convection, Marangoni convection, convection due to the motion of the mechanical barrier of the Langmuir trough, and artificial convection caused by an electromagnetic stirrer cannot produce desorption rates of the observed magnitude. These findings convincingly prove for the first time that the convective diffusion has less of a role in the transport process than previously thought. The most likely reason for the acceleration is identified as leakage through the movable barrier. The rate of this leakage is estimated form the experimental data. Implications for the use of adsorption isobars to study desorption kinetics are discussed.

Zeolite/Cellulose Acetate (ZCA) in Blend Fiber for Adsorption of Erythromycin Residue From Pharmaceutical Wastewater: Experimental and Theoretical Study.

The expanding amount of remaining drug substances in wastewater adversely affects both the climate and human well-being. In the current investigation, we developed new cellulose acetic acid derivation/zeolite fiber as an effective technique to eliminate erythromycin (ERY) from wastewater. The number of interchangeable sites in the adsorbent structures and the ratio of ERY to the three adsorbents were identified as the main reasons for the reduction in adsorption as the initial ERY concentrations increased. Additionally, for all adsorbents, the pseudo–second-order modeling showed better fitting for the adsorption than the pseudo–first-order modeling. However, the findings obtained in the pseudo–first-order model were still enough for explaining the sorption kinetics of ERY, showing that the surface displayed all chemisorption and physi-sorption adsorption processes by both adsorbents. The R 2 for the second order was very close to 1 for the three adsorbents in the case of pseudo–second-order. The adsorption capacity reached 17.76 mg/g. The three adsorbents showed negative values of ΔH, and these values were −6,200, −8,500, and −9600 kJ/mol for zeolite, CA, and ZCA, respectively, and this shows that the adsorption is exothermic. The desorption analysis shows no substantial loss of adsorption site after three trials, indicating higher stability and resilience of the three adsorbents, indicating a strong repeatability of their possible use in adsorption without contaminating the environment. In addition, the chemical attitude and possible donor–acceptor interactions of ERY were assessed by the quantum chemical parameters (QCPs) and NBO analysis performed, at the HF/6-311G** calculations.

Adsorption of neutral red dye by chitosan and activated carbon composite films

Research indicates the use of adsorbent materials to remove pollutants from wastewater and effluents, which can be obtained from renewable materials such as biomass, biopolymers (chitosan) or composites. Thus, the objective of this work was to produce and evaluate activated carbon (AC) and chitosan composite films as adsorbents of neutral red dye. AC films were produced using CO2 and water vapor. The variables of the activation process were time (1 and 2 h) and temperature (600 and 750 °C). Five films were produced, with one pure chitosan (T1) film and four activated carbon with chitosan films (T2, T3, T4 and T5). The T2 film refers to activated carbon produced at 600 °C for 1 h + chitosan, T3 to activated carbon produced at 600 °C for 2 h + chitosan, T4 to activated carbon produced at 750 °C for 1 h + chitosan and T5 to activated carbon produced at 750 °C for 2 h + chitosan. The T5 film increased its adsorption capacity by approximately 87% and its removal efficiency of neutral red dye by 43% compared to T1. The presence of activated carbon in the films provided an increase in the adsorption capacity of the neutral red dye.