Optimal Modification Conditions Research Articles

Optimal conditions of acid modification of Bentonite-Like Clay

The results of mathematical modeling of the bentonite-like clay’s process of modifying various concentrations sulfuric acid depending on time the modification process is given in the presented article. As a result, the optimal parameters of this process were determined by the experimental and calculation method.

Catalytic Ozonation with Activated Carbon for Degradation of Polyacrylamide in Wastewater

With the development of tertiary oil, the technology of polymer oil displacement has been widely used. The treatment of the oilfield wastewater become harder, owing to the extensive use of the polyacrylamide (PAM) in oil displacement. This experiment explored the modified activated carbon surface properties on the removal rate of PAM, under the conditions of the temperature 50 °C, the ozone concentration 5 L/min, the reaction time 1 h . The activated carbon(AC) was modified by copper, iron, nitrogen-containing compound. And the turbidity method was used to analyze the PAM concentration. The experimental results showed that the best modifier was ethylenediamine, which had less nitrogen; the optimum modification conditions of cupric nitrate were the calcination temperature 500 °C, maceration 15 mL; the optimum modification conditions of iron nitrate were the calcination temperature 550 °C, maceration 20 mL.

Enhancement of the Surface Properties on Polypropylene Film Using Side-Chain Crystalline Block Copolymers.

The consumption of polypropylene (PP) has significantly increased over that of other materials because of its light weight, easy molding, and high mechanical strength. However, the applications of PP are limited, owing to the lack of surface properties, especially with respect to adhesive properties and hydrophilicity. In this study, we developed a surface modification method for enhancing the adhesive properties and hydrophilicity on the PP surface using a side-chain crystalline block copolymer (SCCBC). This method was simple and involved the dipping of a PP film in a diluted SCCBC solution. The optimized modification conditions for enhancing the adhesive properties of PP were investigated. The results revealed that the adhesion strength of PP modified with the SCCBC of behenyl acrylate and 2-(tert-butylamino)ethyl methacrylate was enhanced to 2.00 N/mm (T-peel test) and 1.05 N/mm2 (tensile shear test). In addition, the hydrophilicity of PP modified with the SCCBC of behenyl acrylate and di(ethylene glycol)ethyl ether acrylate was enhanced to a water contact angle of 69 ± 4°. Surface analysis was also performed to elucidate a plausible mechanism for PP modification by the SCCBCs. This surface modification method is facile and enhances desirable properties for the wide application of PP.

Modified magnesium hydroxide encapsulated by melamine cyanurate in flame-retardant polyamide-6

In this paper, a novel modified magnesium hydroxide (MH) was successfully prepared with γ-(2,3-epoxypropoxy)propyl trimethoxysilane (KH-560) via the wet process. The optimum modification conditions were obtained as follows: KH-560 dosage of 1.0 wt% at 80 °C for 2 h. The modified MH encapsulated by melamine cyanurate (MCA) at the mass ratio was 1:3. Using polyamide-6 (PA6) as matrix, MCA-MH as flame retardant, a series of flame-retardant PA6/MCA-MH composites were prepared by melt blending and injection molding. The flame retardancy, thermal property, and mechanical properties of PA6/MCA-MH composites were investigated. The investigation results showed that MCA-MH could effectively suppress the melt-dipping behavior and reinforce flame retardancy of PA6. PA6/MCA-MH composites successfully passed the vertical combustion (UL-94) V-0 rating and limiting oxygen index (LOI) as high as 32.5% with the incorporation of 20 wt% of MCA-MH. The residues of the PA6/MCA-MH composites were increased with the increasing MCA-MH. What’s more, the mechanical properties of the composites were also enhanced because of MCA-MH had better compatibility and dispersion in the PA6 matrix compared with MH. Therefore, PA6/MCA-MH composites with excellent flame retardancy while have maintained optimal mechanical properties can be obtained.

Adsorption of Bisphenol A from Aqueous Solution by HDTMA-Tunisian Clay Synthesized Under Microwave Irradiation: A Parametric and Thermodynamic Study

AbstractBisphenol A (BPA), an endocrine disrupting compound, is of concern because of its wide presence throughout the environment and its harmful effects. The present study aimed to prepare an eco-friendly, low-cost, and efficient adsorbent for removal of BPA from wastewater. A natural Tunisian clay was used as a raw material. First, the clay was purified and then modified with hexadecyltrimethylammonium bromide (HDTMA) using microwave heating. The optimal conditions for clay modification were as follows: activation ratio = 0.3:(g/g), solid/liquid ratio = 5%, and microwave heating condition (2:min, 100:W). The purified and modified clays, abbreviated as HP and HMH, respectively, were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption/desorption analysis (BET). Adsorption tests were conducted in a batch reactor process under various conditions. The tests showed that the BET specific surface area of HMH is considerably smaller than that of HP, whereas the basal spacing increased from 14.99 to 22.07 Å after modification, indicating the success of HP organophilization. The adsorption of BPA onto HMH was not affected by the pH of solution between 2 and 10 and only slightly by temperature variation from 23 to 50°C, but was affected significantly by the initial concentration of BPA, contact time, and organo-clay dose. At equilibrium, the data obtained were fitted to Langmuir and Freundlich models. The best fit was obtained by the Langmuir model with a maximum monolayer adsorption capacity of 217.39 mg/g at 23°C. The thermodynamic study suggested that the removal of BPA by HMH was spontaneous (ΔG < 0), exothermic (ΔH < 0), and favorable. The present study demonstrated that HMH synthesized from an abundant and cheap natural clay could be used successfully as a low-cost adsorbent for the removal of BPA from wastewater.

Study on surface modification of attapulgite

In this study, the surface modification of attapulgite was studied. Firstly, the experiment of acid roasting was carried out. The morphology and composition of attapulgite before and after modification were systematically studied by means of SEM, TEM and FTIR. The results showed that the optimal experimental conditions for modification were hydrochloric acid acidification, the concentration was 1 M, the acidification time was 4 h, and the temperature was 75 °C.The thermal activation conditions were determined to be 420 °C roast for 2 h. Attapulgite was successfully modified, and its specific surface area ratio increased greatly, from 144.29 m2g−1 to 187.87 m2g−1. In this study, the attapulgite with high specific surface area prepared is of great significance for the further use of attapulgite with high added value.

Ultrasound for pectinase modification: an investigation into potential mechanisms.

Today, ultrasound is increasingly utilized in enzyme modification. Strongly dependent on the specific operational conditions, the modification effect brought by ultrasound can be activation and inactivation of enzymes. This work aims to study the ultrasound mechanisms under different conditions, to investigate the respective roles of free radical effect and mechanical effect in pectinase activation and inactivation, and to reveal the influence of pectinase concentration on the ultrasound-modification effect. When ultrasound was introduced to a liquid system, generation of free radicals was positively correlated with ultrasound intensity and treatment duration, but negatively correlated with temperature. Thiourea with a concentration of 4 mmol L-1 was selected as a free radical scavenger to effectively shield ultrasound free radicals. The highest enzyme activity of pectinase solutions at 0.1, 1.0, and 10.0 mg mL-1 was obtained at the same ultrasound intensity of 4.50 W mL-1 and time of 15 min, where the enzyme activity was increased by 68.24%, 20.98% and 18.83%, respectively. Furthermore, the addition of thiourea enhanced the enzyme activity at each tested ultrasound intensity and time, especially those exceeding the best conditions; it also eliminated the redshift phenomenon that was previously presented in the fluorescence spectra of pectinase samples. Pectinase concentrations did not change the optimum ultrasound conditions for enzyme modification, but pectinase with a low concentration was more vulnerable to ultrasound treatment. During modification, ultrasound mechanical effects dominated in the pectinase activation, while free radical effects dominated in the inactivation process. © 2020 Society of Chemical Industry.

Study on Preparation and Application of Protein Filler by Chitosan Modified Keratin

In order to make rational use of waste cattle hair, the protein filler was prepared by using chitosan modified keratin which hydrolyzed waste cattle hair, then used in retanning and filling process. The optimal modification conditions of keratin: chitosan: keratin was 20:80, pH value was 2, time was 5h, chitosan modified keratin product zeta potential was 31.3mV, nanometer particle size was 482d·nm. Chitosan-modified keratin can be used as chrome auxiliaries in the retanning process to significantly reduce total chromium in the waste liquid. At the same time, the modified keratin had good filling performance. Moreover, the softness, tearing force and tensile strength of the shoe upper leather which filled with chitosan modified keratin were improved.

Antibacterial efficacy of chitosan- and poly(hexamethylene biguanide)-immobilized nanofiber membrane

In this study, polyacrylonitrile (PAN) nanofiber membrane was prepared by an electrospinning technique. After alkaline hydrolysis, the ion-exchange nanofiber membrane (P-COOH) was grafted with chitosan molecules to form a chitosan-modified nanofiber membrane (P-COOH-CS). Poly(hexamethylene biguanide) (PHMB) was then covalently immobilized on P-COOH and P-COOH-CS to form P-COOH-PHMB and P-COOH-CS-PHMB, respectively. The nanofiber membranes were subjected to various surface analyses as well as to the evaluations of antibacterial activity against Escherichia coli. The optimal modification conditions for P-COOH-CS-PHMB were attained by water-soluble chitosan at 50 kDa of molecular weight, coupling pH at 7, and 0.05% (w/w) of PHMB. Within 10 min of treatment, the antibacterial rate was close to 100%. Under the similar conditions of antibacterial treatment, the P-COOH-CS-PHMB exhibited a better antibacterial efficacy than the P-COOH-PHMB. When the number of bacterial cells was increased by 2000 folds, both types of nanofiber membranes still maintained the antibacterial rate close to 100%. After five cycles of repeated antibacterial treatment, the antibacterial efficacy of P-COOH-PHMB was 96%, which was higher than that of P-COOH-CS-PHMB (83%). The experimental results revealed that the PHMB-modified nanofiber membranes can be suitably applied in water treatment such as water disinfection and biofouling control.

Fabrication of a Zr-based bulk metallic glass surface with extreme wettability

Unlike the high surface energy of traditional metallic materials, metallic glass with amorphous structure have a lower surface energy with a different wettability of solid surfaces. In this work, the micro-nano hierarchical structures were constructed on the Zr55Cu30Ni5Al10 bulk metallic glass (BMG) surface by electrochemical corrosion and then modified with stearic acid to form both superhydrophobic and superlipophilic surfaces. After the optimized modification conditions, the water contact angle was as high as 169.6 ± 3.5° with a low water sliding angle of 5° and the contact angle of oil on the alloy surface was 5°, respectively. The present work would open a window for the application of bulk metallic glasses in nondestructive liquid transportation and oil-water separation.

Adsorption of Acid Orange Ⅱ with Two Step Modified Sepiolite: Optimization, Adsorption Performance, Kinetics, Thermodynamics and Regeneration.

In this study, a two-step modification of sepiolite for adsorption enhancement was investigated. The cetyltrimethylammonium bromide (CTAB) was utilized for the organic modification process after a heat modification. To develop the optimal modification condition, adsorption of Acid Orange II onto modified sepiolite was investigated with respect to heat temperature and adsorbent dosage. The temperature of 200 °C and 100% cation exchange capacity (CEC) was deemed as the optimal condition. The impacts of operation conditions on adsorption procedure, including pH, adsorbent dosage and adsorption duration, were comprehensively discussed. The adsorption of Acid Orange II by sepiolite is in accordance with the quasi-secondary kinetic model. Moreover, the results of intraparticle diffusion indicate that the intraparticle diffusion was the dominant adsorption force in the initial adsorption period. The adsorption process was obeyed with the Langmiur adsorption model. The results from regeneration procedure suggest that the superior regeneration obtained with 0.8 mol/L NaOH concentration.

Влияние модифицирования наноалмаза на смачиваемость поверхности оптического кислородного датчика и биологическое обрастание при длительных измерениях in situ

Предложен способ управления смачиваемостью поверхности фторированного материала и контроля биообрастания за счет внедрения в структуру модифицированного наноалмаза. На примере сенсора молекулярного кислорода с помощью комплекса методов определены оптимальные условия модифицирования, не приводящие к изменению прочих функциональных свойств материала, таких как градуировочная зависимость и время отклика. Испытания in vitro показали, что небольшое количество аминированных наноалмазов придает поверхности бактерицидные свойства, но при большом содержании, напротив, наблюдается улучшенная адгезия биоматериала за счет уменьшения гидрофобности. Длительные испытания in situ в условиях, симулирующих биореактор с активно растущей биомассой, продемонстрировали практически полное отсутствие биологического обрастания у модифицированного материала и значительное обрастание сенсора из традиционно применяемого полистирола.

Caffeine determination in beverages by voltammetry with the carbon-containing electrodes modified with aryldiazonium salts

The method of carbon containing electrode ( CCE ) modification with tosylated arendiazonium salts ( ADT ) was proposed for the voltammetric ( VA ) determination of caffeine in beverages. The comparison of chemical spontaneous and electrochemical modification approaches was carried out for ADT modified CCE for VA caffeine determination for the first time. A new class of ADT is characterized by high solubility and stability for one month that plays significant role in the process of electrode surface modification. Salts with nitro and carboxy substituents were tested. The optimal conditions for the spontaneous chemical modification of the CCE were selected: ADT modifier with NO 2 substituent, electrode immersion time in the modifier solution for 10 seconds, modifier concentration of 5 mg / dm 3 . ADT deposition on the electrode surface was confirmed by the IR spectroscopy and scanning electron microscopy with the formation of covalent bonds between the carbon atoms of electrode surface and the benzene rings of the modifier. It was shown that the electroactive surface area increases by two times after the modification. Consequently, the technique sensitivity increasing the detection limit of 51 mg / dm 3 and linear range extension from 154 up to 500 mg / dm 3 was observed. While applying the modified electrode, the analysis time was reduced to 15 minutes. Furthermore, the suitability of CCE modified with NO 2 substituent was tested for the analytical purposes. As a result, the caffeine was determined in some tonic and carbonated drinks. The comparison of the results obtained by the proposed method with ADT modified CCE and the level declared by the manufacturer was carried out. The high compliance was established. In addition, the obtained data was consistent with the results by the independent spectrophotometric method. Keywords : caffeine, diazonium aromatic salts, modifier, carbon-containing electrode, voltammetry, spontaneous modification, SEM, IR spectroscopy, cyclic voltammetry DOI: http://dx.doi.org/10.15826/analitika.2020.24.1.007 E.V. Dorozhko, A.O. Gusar, E.A. Bedareva, G.B. Slepchenko, M.E. Trusova, E.I. Korotkova National Research Tomsk Polytechnic University, Lenina prosp., 30, Tomsk, 634050, Russian Federation

Surface modification of pine bark with quaternary ammonium groups and its use for vanadium removal

Chemically modified pine bark was synthesized by using glycidyl trimethyl ammonium chloride (GTMAC) in the presence of sodium hydroxide. Optimization of the modification parameters was performed in order to maximize vanadium removal. Parameters included the initial NaOH concentration (0.01–2% w/v), GTMAC dosage (0.0067–0.0805 mol/g), modification time (1–6 h), modification temperature (40–80 ℃) and volume (25–100 mL). The optimal modification conditions were found to be 0.1% NaOH (w/v), 0.0134 mol/g GTMAC, 3 h and 60 ℃. The initial NaOH concentration played the most important role in successful modification while the GTMAC/NaOH ratio and volume had no significant effect under the studied conditions. Leaching of organic substances from the modified product was minor in comparison with raw pine bark. XPS analysis confirmed that quaternary nitrogen was successfully grafted onto the pine bark and that the BET surface area increased in the modification. The maximum vanadium adsorption capacity of the optimized product was found to be 32.3–35.0 mg/g at different temperatures (20 ℃, 15 ℃ and 5 ℃) at pH 4 with a contact time of 24 h, and the adsorption data was in very good agreement with the Freundlich and Redlich-Peterson models. The adsorption kinetics can be described well by the Elovich equation. Fitting the kinetic data with intra-particle diffusion and Boyd models showed that the adsorption process was controlled by both film and intra-particle diffusion, while intra-particle diffusion was the rate-limiting step. Regeneration studies demonstrated that, as a recyclable product, modified pine bark can be used effectively in real industrial processes for vanadium removal.

BIOCONVERSION OF SECONDARY PRODUCTS OF PROCESSING OF GRAIN CEREALS CROPS

A method has been developed for the production of organic ingredients from secondary products resulting from the high-quality grinding of triticale and wheat into flour, which involves the enzymatic action of amylolytic enzymes to release starch polysaccharides while preserving the native properties of dietary fibers and biologically active substances associated with them. To a large extent, the features of the properties of the obtained ingredients are due to the number and composition of the components of dietary fiber of grain, as well as the morphological features of their structure. It is shown that the viscosity of aqueous colloidal systems at a concentration of soluble dietary fiber of the ingredient 0.5 % increases 11 times; at a concentration of 1.0 % — 30 times, forming a viscous gel-like structure. This allows them to be used for gelling, thickening and stabilization of aquatic food systems. The use of ingredients with a high content of NLP in baking is possible only taking into account their water absorption capacity. A method for the enzymatic modification of secondary products of processing of grain triticale was developed. On the basis of the study of the kinetics and efficiency of the effect of proteolytic and cellulolytic enzyme preparations (EP) and their compositions, optimal conditions for enzymatic modification (the EP dosage is 0.5…0.75 units of PA/g of bran, 0.3…0.4 units of CA/g of bran, the optimum temperature is 40–50 °С, pH is 5.0 and 3.5, the duration of reactions is 1.5 hours) have been determined. The use of cellulolytic EP allowed to increase the amount of reducing substances and soluble protein by 1.5–2.5 times in comparison with the control sample. The biomodified bran obtained using the MEC «Shearzyme 500 L» + «Neutrase 1.5 MG» and «Viscoferm L» + «Distizym Protacid Extra» has a high degree of hydrolysis of non-starch polysaccharides and proteins, is characterized by a certain ratio of high-, medium-, low-molecular peptides and amino acids, has different functional and technological properties. They can be used in the production of a wide range of general-purpose, functional and treatmentand-prophylactic food products.

Study on modification of rabbit hair fibers with L-cysteine

Rabbit hair fibers were modified by L-cystine under the action of ultrasound and a kind of modified rabbit hair fiber was obtained. An orthogonal test of four factors and three levels was designed. The range analysis was analyzed using a comprehensive score method of friction factor and fiber strength, and the variance analysis was carried out by Statistical Package for Social Science statistical software. The optimal modification conditions were obtained: a concentration of L-cystine (A) of 0.05 mol/L, ultrasonic power (B) of 90 W, a water bath temperature (C) of 75℃, and ultrasonic treatment time (D) of 1 hour. Univariate analysis showed the L-cystine concentration had the most significant effect on the modification of rabbit hair fibers, and the regression equation is y = 74.423 + 1300.267 A−1.818 C−9092A2 + 0.019C2. The surface brightness of the modified rabbit hair fibers was enhanced and the scale angle was increased 20° by setting up the angle of the scale model and the electron microscope. The internal structure of rabbit hair fibers was characterized by Fourier transform infrared spectroscopy, peak separation, and differential scanning calorimetry. The results showed that L-cystine reduced the disulfide bond in the macromolecular chain by 3%, resulting in a change in the secondary structure of the rabbit hair, a decrease in the α-helix structure content, and an increase in β-folding structure content. Ellman’s reagent was used to determine that the content of the sulfhydryl group consumed in the modification was 0.211 mol/L. Testing the dye adsorption capacity and spinnability (adding 20%) of modified rabbit hair fibers showed an obvious improvement.

Using microwave-assisted phosphorylation to improve foaming and solubility of egg white by response surface methodology

The purpose of this study was to establish optimal conditions for microwave-assisted phosphorylation modification of egg white. Response surface methodology was used to model and optimize the degree of phosphorylation, solubility, foaming ability, and foaming stability of egg white powder. The concentration of sodium tripolyphosphate, microwave power, and microwave time were selected as the main processing conditions in the phosphorylation modification of egg white protein. The following 3 conditions for optimal phosphorylation modification of egg white are the concentration of sodium tripolyphosphate of 33.84 g/L, microwave power of 419.38 W, and microwave time 90 s for maximum functional properties (solubility, foaming ability and foaming stability) and the concentration of sodium tripolyphosphate of 32.97 g/L, microwave power of 429.29 W and microwave time of 90 s for maximum foaming properties (foaming ability and foaming stability), respectively. We consequently succeeded in phosphorylation modification with microwave assistance and confirmed the various desirable properties of optimal phosphorylation modification.

Optimization of 3-aminopropyltriethoxysilane functionalization on silicon nitride surface for biomolecule immobilization

The 3-aminopropyltriethoxysilane (APTES) is a common method for biomolecule immobilization on silicon and silicon derivatives such as silicon nitride (Si3N4). However, there are many parameters which impact the efficiency of APTES modification such as APTES concentration and reaction time. Thus, various APTES concentrations (0.1%, 0.5%, 1%, 2%, 5%, and 10%) under different reaction times (15, 30, 60 and 120 min) were compared to achieve the optimal APTES modification condition which produced a thin and stable APTES layer on Si3N4 surface. The modified surfaces were characterized by contact angle (CA) measurement, Fourier transform infrared (FTIR) spectroscopy and spectroscopic ellipsometry to determine the wetting property, chemical bonding composition and surface thickness, respectively. In addition, biotin was used as a model to determine the effectiveness of APTES modification condition by coupling with glutaraldehyde (GA). The Alexa Flour 488 conjugated streptavidin was performed to visualize the presence of biotin using fluorescence microscopy due to the specifically binding between biotin and streptavidin. The atomic force microscopy (AFM) was utilized to determine the surface topology which was an indicator to demonstrate the agglomeration of APTES molecule. Moreover, ion sensitive field effect transistor (ISFET) was employed as a biosensor model to demonstrate the effect between surface thickness and sensitivity of biosensor. The results show that the APTES thickness is directly correlated to the APTES concentration and reaction time. Since the importance parameter for ISFET measurement is the distance between biomolecule and sensing membrane of ISFET, the thicker APTES layer negatively impacts the sensitivity of ISFET based biosensor because of the ion shielding effect. Therefore, these results would be valuable information for development of Si3N4 biosensor, especially ISFET based biosensor.

Chemically engineered biochar – Effect of concentration and type of modifier on sorption and structural properties of biochar from wood waste

The main aim of study was a) preparation of biochars (BCs) engineered chemically with various reagents including base (NaOH), as well as mineral (HCl, HNO3, H2SO4) and organic (CH3COOH) acids, b) determination of type and concentration effect of the modifier on surface properties of the BCs, and c) assessment of optimal modification conditions regarding environmental aspects. Results showed that modifiers used at the lowest concentration (0.001 M and 0.01 M) changed the BCs properties insignificantly. Modification with 0.1–1.0 M NaOH caused increase of value of surface area (by 21–82%) and volume of pores from 5 to 40 nm (by 109–239%). Acidic modifiers at 0.1–1.0 M enhanced the number of acidic functional groups, mainly lactonic ones. The best effect was obtained for BCs treated with CH3COOH and H2SO4, revealing an elevation of acidic structures by 13–17% and by 9–15%, respectively. The largest enhancement of basic groups occurred for the BCs treated with increasing concentration of NaOH (by 21–154%) and CH3COOH (by 2–50%). The pH of the modified BCs was drastically reduced/elevated after treating with the highest acid/base concentrations, which suggests considering compromise between the best chemical properties of BC and its safe use, e.g. selection of the BC modified with 0.1 M modifier.

The Effect of Modified Nanodiamonds on the Wettability of the Surface of an Optical Oxygen Sensor and Biological Fouling During Long-Term in Situ Measurements

A method is proposed for controlling the wettability of the surface of a fluorinated material and for controlling its biofouling by introducing modified nanodiamonds into the structure. The optimal modification conditions were determined by means of a set of methods based on the example of a molecular oxygen sensor. They do not lead to a change in other functional properties of the material, such as the calibration curve and response time. In vitro tests have shown that a small amount of aminated nanodiamonds gives the surface bactericidal properties, but with a high content, improved adhesion of the biomaterial is observed due to a decrease in hydrophobicity. Long-term in situ tests under conditions simulating a bioreactor with actively growing biomass showed an almost complete absence of biological fouling of the modified material and revealed a significant fouling of the sensor from traditionally used polystyrene.