Initial Salicylic Acid Concentration Research Articles

Alginate and pectin films covering halloysite with encapsulated salicylic acid as food packaging components

Bionanocomposites containing biopolymers and inorganic nanomaterials of natural origin are intensively studied as eco-firendly alternative to non-biodegradable materials for food packaging applications. The preparation and characterization of pectin and alginate films filled with halloysite (Hal) loaded with salicylic acid are presented here. Two types of Hal with different morphology, derived from Dragon and Dunino mines, were used for adsorption of the antimicrobial agent. The adsorption properties of the nanomaterials were comparable after their initial activation with sulphuric acid. The adsorption increased with increasing initial concentration of salicylic acid. The theoretical analysis of experimental data indicated good correlation with Freundlich isotherm and pseudo-second-order kinetic models. The in vitro release profiles differed depending on the type of biopolymer and the release medium. The release rates were slightly lower for materials with Hal Dunino than those of Hal Dragon in 20% v/v ethanol. Cumulative release was more controlled and prolonged with alginate films, especially in 50% v/v ethanol mimicking food with lipophilic properties. Moreover, alginate films demonstrated greater antimicrobial activity against selected food spoilage bacteria. Alginate materials were effective against four bacteria strains, while pectin films showed the ability of growth inhibition of only two strains tested.

Microwave catalytic activities of supported perovskite catalysts MOx/LaCo0.5Cu0.5O3@CM (M = Mg, Al) for salicylic acid degradation

Three-dimensionally (3D) meso-macroporous LaCo0.5Cu0.5O3@CM and MOx/LaCo0.5Cu0.5O3@CM (M = Mg, Al) perovskites were synthesized by impregnation of carbon microsphere (CM) templates and calcination method. The obtained perovskites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and microwave network analysis. The composite catalysts were prepared for the microwave (MW)-induced H2O2 catalytic degradation of salicylic acid (SA) as a target contaminant in aqueous solution. Results showed that Al2O3/LaCo0.5Cu0.5O3@CM displayed higher microwave catalytic activity than MgO/LaCo0.5Cu0.5O3@CM, which was closely related to its higher active species concentration, better microwave absorbing ability and the interaction between Al2O3 and LaCo0.5Cu0.5O3@CM. Moreover, the degradation kinetics could be well fitted by the pseudo first-order kinetic model. As the increase of MW power, initial pH, dosage of catalyst and H2O2 concentration, its SA degradation rate first increased and then decreased, while the initial SA concentration declined continuously. The introduction of metal oxides increases the mobility of the surface oxygen, playing a crucial role in surface oxygen species generation. The enhancement of catalytic activity could be mainly ascribed to the OH activation process under MW irradiation. After five reaction cycles, the stability and reusability remained high. The overall findings provide new insight into Al2O3/LaCo0.5Cu0.5O3@CM under MW irradiation for the degradation of SA and other relevant organic pollutants.

Enhanced catalytic activity of templated-double perovskite with 3D network structure for salicylic acid degradation under microwave irradiation: Insight into the catalytic mechanism

Salicylic acid (SA) is considered as a priority pollutant due to its physiological toxicity and pseudo-persistence in the environment. In this study, a new catalytic degradation technology using microwave (MW) induced templated-double perovskite was proposed and applied in the treatment of SA in aqueous solution. A series of LaCo1-xCuxO3@PMMA (X = 0, 0.3, 0.5, 0.7, 1) perovskite-type catalysts with three-dimensionally porous network structure were synthesized by polymethylmethacrylate (PMMA) templating method, and characterized by scanning electron microscopy (SEM), N2 adsorption-desorption analysis (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and microwave network analysis. The results showed that the addition of PMMA template and substitution with Cu (x = 0.5) were beneficial to the generation of LaCo0.5Cu0.5O3@PMMA with high catalytic activity, which possessed unique 3D porous network structure, smaller particle size distribution, better microwave absorbing performance and higher ratios of Co3+/Co2+ and Oads/Olatt. The SA removal fit pseudo-first-order model, and its degradation efficiency increased firstly and then decreased with the increase of MW intensity, solution pH and catalyst dosage, while decreased as initial SA concentration increasing. The LaCo0.5Cu0.5O3@PMMA catalyst presented favorable recycling and stability in the repeated experiment. The excellent catalytic activity was attributed to both active species and MW “hot spots”, among which OH and hvb+ played main roles in the catalytic process, and MW “hot spots” effect had a small contribution to the degradation. Hence, LaCo0.5Cu0.5O3@PMMA/MW technology with rapid degradation and negligible secondary pollution provides a potential way for treating salicylic acid in water.

A supported dendrimer with terminal symmetric primary amine sites for adsorption of salicylic acid

The aim of this work is to evaluate the uptake of salicylic acid (SA), an emerging pollutant, using a nano-polar dendrimer containing highly branched terminal symmetric amine groups immobilized on mixed-oxide nanoparticles of SiO2-Al2O3. Several variables, including the effect of initial SA concentration, contact time, temperature, initial pH, adsorbent dosage, interfering ions, and the hydrophobicity of the adsorbent (SANP-G1.0) were studied. Because of the electrostatic and hydrogen bonding interactions between SA and the amine functional sites of the nano-polar dendrimer, the adsorbent featured a remarkable SA uptake capacity of over 254.5 mg/g after 5 min contact time. The solution pH had a considerable impact on SA uptake by SANP-G1.0, with optimal uptake occurring around pH 2–5. Kinetic and isotherm studies confirmed that SA removal could be fit with the Sips and pseudo-second-order kinetic models, respectively, implying that a chemical process dominates SA uptake by the SANP-G1.0. The uptake of SA decreased at elevated temperature, demonstrating that this is a chemically and naturally exothermic process between 15 and 80 °C. The uptake efficiency of the reused nanodendrimer was 54% after the tenth adsorption-desorption cycle. Moreover, the SANP-G1.0 showed a high capacity for adsorbing SA from Cayuga Lake water. We studied the possible mechanism of SA uptake, including the effect of interfering ions, using zeta potential, X-ray photoelectron spectroscopy, infrared spectroscopy, and the hydrophobicity of the nanodendrimer. The prepared supported dendrimer, featuring high chemical and mechanical stability, demonstrates good reusability for SA adsorption from aqueous media. An artificial neural network (ANN) model was also designed to simulate SA uptake by SANP-G1.0. The results revealed an excellent fit between the ANN-modeled and experimental data, with a correlation coefficient (R2) of 0.9841.

Adsorption behavior of salicylic acid on biochar as derived from the thermal pyrolysis of barley straws

Abundant wastes of barley straws were utilized as precursor to prepare biochar adsorbent through thermal pyrolysis. Pore characteristics, morphology, and attraction extent of the prepared adsorbent toward salicylic acid were identified. The obtained biochar had a surface area of 435.52 m2/g, a pore volume of 0.241 cm3/g, and an average pore width of 22.16 Å. The effects of batch adsorption variables, such as initial salicylic acid concentration (50–250 mg/L), contact time (0–24 h), initial pH (3–11), and temperature (25 °C–45 °C) on the biochar performance were tested. Equilibrium data analysis revealed the best correlation of the Langmuir isotherms, with maximum salicylic acid uptakes of 189.12, 197.43, and 210.56 mg/g at 25 °C, 35 °C, and 45 °C, respectively. The salicylic acid/biochar system exhibited spontaneous, chemisorption, and endothermic natures. Considering its favorable pore characteristics and high attraction performance, barley straw biochar could be a suitable adsorbent to eliminate salicylic acid from wastewaters.

Carbon Bead‐Supported Ethylene Diamine‐Functionalized Carbon Nanofibers: An Efficient Adsorbent for Salicylic Acid

The present study describes the removal of salicylic acid (SA) from water by adsorption using ethylene diamine (EDA)‐functionalized carbon nanofibers (CNFs)‐containing porous carbon beads (∼0.5 mm). Briefly, the phenolic beads, separately synthesized using suspension polymerization, were carbonized and activated. The CNFs were grown on the carbon beads, using chemical vapor deposition, and the prepared fibrous beads functionalized with EDA were used as an adsorbent for SA. The prepared materials were characterized by their physico‐chemical properties, including specific surface area, surface morphology, and surface functional groups. The adsorption tests performed over the initial SA concentration range of 100–1500 mg/L revealed the adsorption capacity of the materials to be ∼682 mg/g, which was considerably larger than that of the adsorbents discussed in the literature for SA. The zeta‐potential analysis attributed enhanced adsorption to the electrostatic interaction and hydrogen bonding between the solute molecules and the EDA‐functionalized surface of the CNFs. The material and method developed in this study for the remediation of the SA‐laden wastewater may be extended to other acidic pollutants present in pharmaceutical effluents.

Adsorptive Removal of Salicylic Acid from Aqueous Solutions using New Graphene-Based Nanosorbents

In the present research, new carbon nanosorbents were developed for removal of salicylic acid (SA) in aqueous media. The starting materials were graphene flakes with thicknesses of 12 nm (C12) and 60 nm (C60) subjected to covalent functionalisation in a reflux reactor using different chemical reagents (HNO3,H2SO4, NaOH and KOH) at 353 K for 4 h. Characterisation work revealed that the specific surface areas of C12 and C60 were 68.74 and 9.76 m2/g, respectively. The capability of the prepared nanosorbents in SA sequestration was examined using batch adsorption system. The results suggested that C12 treated withH2SO4 (C12-H2SO4) exhibited the highest percentage removal of SA (55 %). FTIR analysis showed the presence of various functional groups viz. hydroxyl, alkyne, amine, carboxylic acid, carbonyl, alcohol and alkyl halide on C12-H2SO4 which might have interacted with SA. The adsorption equilibrium was evaluated by varying the initial SA concentration. Experimental data were analysed by Langmuir, Temkin and Dubinin-Radushkevich (D-R) and Freundlich models. The goodness-of-fit of the models was determined by Marquardt’s percent standard deviation, chi-square, average relative error and sum of absolute error with model parameter optimisation evaluated by sum of normalised errors (SNE). It was found that D-R model was the best fit model with the lowest SNE. The primary results showed that chemical functionalisation has been successfully used for attaching specific functional groups onto C12. In addition, the new graphene- based nanosorbent viz. C12-H2SO4 has a great potential application for SA removal.

Quaternized Three-Dimensionally Ordered Macroporous Cross-Linked Polystyrene and its Adsorption Character toward Salicylic Acid in Aqueous Solution

Three-dimensionally ordered macroporous cross-linked polystyrene loaded with quaternary ammonium groups (3DOM CLPS-QA) was prepared for using as a novel adsorbent. The performance of 3DOM adsorbent was evaluated by adsorbing salicylic acid (SA) in aqueous solution. Adsorption isotherm and kinetics were investigated under different temperatures (293 K, 303 K, 313 K). The rising temperature led to a significant increase in the adsorption capacity towards SA, and 3DOM CLPS-QA exhibited a high adsorption capacity (317.86 mg/g when the initial concentration of SA was 500 mg/L at 303 K). Moreover, the effect of solution pH on adsorption indicated that the charge interaction was the dominating driving force for the adsorption of SA onto 3DOM CLPS-QA from the aqueous solution. The 3DOM adsorbent was also reusable and could be regenerated by 0.1 M hydrochloric acid solution. After reusing for six times, the adsorption capacity still maintained about 80% of the original capability.

太阳光响应型Ag 2 S/Ag 3 PO 4 复合材料的制备及催化降解水杨酸

以AgNO 3 ，Na 2 HPO 4 和硫粉为原料，采用共沉淀-水热法合成了具有太阳光响应型Ag 2 S/Ag 3 PO 4 复合材料，运用扫描电子显微镜（SEM）、X射线粉末衍射（XRD）、X射线光电子能谱（XPS）和紫外-可见漫反射（UV-VisDR）光谱等方法对样品进行了表征，并在模拟太阳光条件下，考察了Ag 2 S/Ag 3 PO 4 对水杨酸的光催化降解效率.结果表明，与Ag 3 PO 4 相比，Ag 2 S的负载量为1%（质量分数）时Ag 2 S/Ag 3 PO 4 粒径变小，呈立方晶相结构；Ag 2 S/Ag 3 PO 4 复合材料可以有效促进光生电子-空穴分离，使Ag 3 PO 4 禁带宽度降低到2.24eV，并增强了可见光的吸收能力.在Ag 2 S负载量为1%，120℃水热4h条件下，Ag 2 S/Ag 3 PO 4 复合材料具有最佳光催化活性，经模拟太阳光照射60min对10mg/L的水杨酸去除率达到88.2%.

Electrochemical assisted photocatalytic degradation of salicylic acid with highly ordered TiO2 nanotube electrodes

To explore the kinetics of photoelectrocatalytic degradation of salicylic acid, one of the important PPCPs, highly ordered TiO2 nanotube arrays (NTs) were prepared by the electrochemical anodization and characterized with scanning electron microscopy and X-ray diffraction techniques. The effect of TiO2 NTs properties, bias potential, initial salicylic acid concentration and solution pH on the degradation efficiency was studied and carefully analyzed. The results revealed that the salicylic acid degradation follows quasi-first order kinetics in the photoelectrocatalytic process, and the fastest decay kinetics was achieved in acidic environment (pH 2). The result was further interpreted through the electrochemical impedance spectroscopy. It is confirmed that the electrochemical assisted photocatalysis is a synergetic approach to combat stable organic substances with improved efficiency.

A flat-sheet supported liquid membrane based on Aliquat® 336 as carrier for the removal of salicylic acid from aqueous solution

This study deals with the extraction of salicylic acid (SA) from aqueous solutions through a flat-sheet supported liquid membrane system. Tricaprylmethylammonium chloride (Aliquat® 336) diluted in 2-octanol is used as membrane organic phase. In a previous work, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim][PF6]) or ethylammonium nitrate (EAN) is used instead of the above mixture. Transport efficiency around 50% and 9 days stability has been obtained. In this work, the use of 10% (v/v) Aliquat® 336 in 2-octanol improves the transport efficiency of the system (around 90%). The important operational variables affecting the facilitated transport of SA are concentration of Aliquat® 336, membrane viscosity, feed phase pH, stripping agent concentration, initial SA concentration, polymeric support type, and membrane stability. Regardless of its higher SA transport efficiency, the SLM based on the mixture Aliquat® 336/2-octanol exhibits shorter long-term stability (time dependent-negative tendency) as compared to the use of [C6mim][PF6] or EAN.

Enhanced adsorption capacity and selectivity towards salicylic acid in water by a cationic polymer functionalized 3-D ordered macroporous adsorbent

3-D ordered macroporous (3DOM) materials have exhibited advantages in the adsorption field. Their monodisperse macropores undergo facile modification, and the interconnected cavities enhance accessibility to the active sites, while the short diffusion path of the thin pore walls accelerates material exchange. A 3DOM material can increase the number of adsorption sites by the grafting of a polymer chain with functional groups from the pore wall of the 3DOM resin. In this study, different amounts of the cationic polymer poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) were grafted from the pore wall of a 3DOM cross-linked polystyrene (3DOM CLPS-g-PDMAEMA) via surface-initiated atom transfer radical polymerization (SI-ATRP) and salicylic acid (SA) was employed as the model adsorbate. PDMAEMA chains can adopt a more extended conformation in water. Therefore, the adsorption capacity increases with the grafted amount due to the increasing number of adsorption sites and the extended chain conformation. The 3DOM CLPS-g-PDMAEMA exhibits a very high adsorption capacity towards SA (390 mg g−1 when the initial concentration of SA is 500 mg L−1) which is even higher than that of activated carbon. Moreover, the 3DOM adsorbent also exhibits a high adsorption selectivity between SA and phenol, and the selectivity coefficient for SA reaches 45.8 in the presence of phenol. The 3DOM adsorbent is also reusable and can be regenerated by sodium hydroxide solution. The results of fifteen adsorption–desorption cycles show that all the adsorption capacities maintain above 85% of the original SA loading capacity. We envision that novel 3DOM polymeric adsorption will play a significant role in developing a new generation adsorbent.

Kinetic study on the photocatalytic degradation of salicylic acid using ZnO catalyst

The photocatalytic degradation of salicylic acid was studied by a batch process using ZnO as the catalyst on irradiation with UV light. The effect of process parameters such as pH, catalyst loading and initial concentration of salicylic acid on the extent of degradation was investigated. The degradation of salicylic acid was found to be effective in the neutral pH range. The optimum catalyst loading was observed at 2.0 g/L. The process followed first order kinetics and the apparent rate constant decreased with increase in the initial concentration of salicylic acid. The mechanism for the degradation of salicylic acid could be explained on the basis of Langmuir–Hinshelwood mechanism. The complete mineralization of salicylic acid was observed in the presence of ZnO photocatalyst. The ZnO was found to be quite stable and undergoes photocorrosion only to a negligible extent.

Atomic layer deposited TiO 2 films in photodegradation of aqueous salicylic acid

Degradation of salicylic acid (SA) with thin film photocatalyst, titanium dioxide (TiO 2), combined with ultraviolet (UV) radiation was studied. Photocatalysts were prepared on glass or silica substrate by atomic layer deposition (ALD) technique. The impact of initial SA concentration (10 and 75 mg/l) and pH (3–10) was studied. Reactions were faster on higher initial SA concentrations and decomposition of SA was greatest at pH 8. Varying deposition temperature and film thickness during ALD process influenced the efficiency of TiO 2. Crystallinity of the film changed with rising deposition temperature (150–450 °C) from amorphous to anatase and further to anatase rutile mixture, where rutile was the dominating phase. SA decomposition rate was greatest with catalysts consisting of both phases whereas pure anatase showed somewhat lesser efficiency and amorphous film did not work at all. Increasing film thickness enhanced the degradation of SA until the film was thick enough. With over 46 nm thick films the results remained the same. Two substrates, glass and silicon, were compared but the material was not found to have any evident impact on the catalytic efficiency of the film.

Anodic oxidation of salicylic acid at Ta/BDD electrode

Boron-doped diamond (BDD) film electrodes using Ta as substrates were employed for anodic oxidation of salicylic acid (SA). The effects of operational variables including initial concentration, current density, temperature and pH were examined. The results showed that BDD films deposited on the Ta substrates had high electrocatalytic activity for SA degradation. There was little effect of pH on SA degradation. The current efficiency (CE) was found to be dependent mainly on the initial SA concentration, current density and temperature. Chemical oxygen demand (COD) was reduced from 830 mg/L to 42 mg/L under a current density of 200 A/m2 at 30 °C.

Degradation of salicylic acid by photo-assisted Fenton reaction using Fe ions on strongly acidic ion exchange resin as catalyst

The photo-assisted Fenton degradation of salicylic acid (SA) was studied by using strongly acidic ion exchange resin (SAIER) exchanged with Fe ions as catalyst in the presence of UV light (254 nm) and H 2O 2. The X-ray photoelectron spectroscopy (XPS) results revealed that the Fe ions are indeed anchored by the sulfonate groups on the surface of the SAIER and are Fe 3+. Our results also indicate that the Fe/SAIER catalyst can significantly enhance the degradation rate of SA without remarkable Fe leaching to the solution, implying that the catalyst has photo-catalytic activity. In addition, the effects of [H 2O 2]/[SA] molar ratio, UVC light power, solution pH, catalyst loading, and initial SA concentration on the degradation of SA were investigated in detail.

Xanthan gum as a carrier for controlled release of drugs.

Systems based on xanthan gum matrix containing 1%, 2% and 5% salicylic acid were prepared and studied as controlled release devices. Swelling of the matrix in distilled water and buffer solutions showed that the ionic strength of the liquid has a strong effect on the sorptive properties of the matrix. From the release experiments, conducted in distilled water at 37 +/- 0.5 degrees C, it was found that the drug delivery process was accomplished within the first 10 hours after immersion and salicylic acid was always released via a non-Fickian transport. The phenomenon can be described by a release exponent (n) in the area of 0.77 independently of the initial concentration of salicylic acid in the xanthan matrix. These results can be interpreted taking into consideration the dimensional and physical changes of the polymeric matrix during swelling.

Photocatalytic degradation of salicylic acid by colloidal Fe2O3 particles

The photocatalytic decomposition of salicylic acid with visible light in an oxygenated aqueous suspension of colloidal α-Fe2O3 particles has been studied. About 10–20 ppm of this organic is degraded within 1 h of irradiation, depending upon the initial salicylic acid concentration. Kinetic parameters have been investigated in terms of a first order rate equation. The rate constant (kap) for this heterogeneous photocatalysis was evaluated as a function of the initial concentration of salicylic acid. Carbon dioxide has been detected over prolonged visible light irradiation. © 1998 Society of Chemical Industry