Alkaline Modification Research Articles

Effect of solvent polarity on the formation of flexible zein nanoparticles and their environmental adaptability

Zein possesses strong self-assembly ability due to its amphiphilicity. To investigate the effect of solvent polarity on both the flexibility of zein and the formation of flexible zein nanoparticles, various ethanol aqueous solutions were chosen. Alkaline modification was applied to improve the flexibility of the zein and a liquid-liquid method was used to produce zein nanoparticles. Solvent polarity plays a positive role in improving the flexibility of zein. Furthermore, native and flexible zein nanoparticles were formed from native zein and flexible zein, respectively. However, nanoparticles could not form from highly flexible zein due to their strong adaptability to changes in solvent. Compared with the emulsifying activity index (EAI) and emulsifying stability index (ESI) of native zein nanoparticles, a higher EAI and ESI of flexible zein nanoparticles were acquired. These results may be attributed to the strong adaptability of flexible zein to the medium changing through changing their secondary structure. Furthermore, the adaptability of flexible zein nanoparticles significantly depended on the initial polarity of the solvent. The deamidation reaction of zein was responsible for the change in zein flexibility. These findings thus provide clear evidence of the relationship between the solvent polarity and structural flexibility of modified zein.

The Influence of Fiber Processing and Alkaline Treatment on the Properties of Natural Fiber-reinforced Composites: A Review

Throughout generations, research on natural fiber-reinforced composites (NFRCs) has been growing and yielding promising results. The notion of blending natural fibers with polymers comes from the composite’s suitable properties, not limited to low density, availability at a low price, biodegradability, and environmental friendliness. The quest for high-performing and marketable NFRCs is driving innovation in the synthesis of such materials. A suitable combination of parameters that optimizes the mechanical and functional properties of the composites without increasing the cost of production is desired. The main objective of this review is to evaluate some of the parameters that influence the behavior and properties of NFRCs. The influence of alkaline modification and natural fiber processing parameters, such as particle size, modification concentration, soaking duration, processing temperature, fiber-to-polymer ratio, and adoption of additives, on composites are discussed. This review summarizes some of the work and provides some directions in the search of an all-around performing economic NFRC.

Synthesis of carboxyl-modified hyper-cross-linked polymers with conspicuous removal capability for various water-soluble contaminants

In this study, we employed hyper-cross-linked porous polymer (HCP-MAH) as precursor to prepare carboxyl-modified hyper-cross-linked polymer (HCP-COOH) through mild alkaline modification. The prepared HCP-COOH had excellent dispersity in water, high specific surface area and abundant pore structures, resulting in highly-efficient adsorption of tetracycline (TC). The TC adsorption capacity of HCP-MAH and HCP-COOH was calculated to be 273.22 mg·g−1 and 418.41 mg·g−1, respectively. Moreover, both of HCP-MAH and HCP-COOH showed excellent adsorption capacities towards dyes and phenols. The electrostatic attraction, pore filling, hydrogen bond, ions exchange and π-π interaction were responsible for TC adsorption. In addition, it was found that the dissolved organic matter (DOM) in the secondary wastewater could promote the removal of TC, which contributed to higher adsorption removal of TC by HCP-MAH and HCP-COOH compared to that in pure water system. This study not only provided a simple method to fabricate an eco-sufficient adsorbent with rich carboxyl groups for TC removal, but also evaluated the application of the adsorbents in the treatment of water-soluble organic pollutants in actual wastewater, which has a great potential in practical use.

Enhanced carbon dioxide adsorption by potassium hydroxide modified peat soil as porous adsorbent

Carbon dioxide (CO 2) capture is a strategy established to mitigate issues related to CO 2 emission through various methods, for instance by adsorption. Soil, a natural resources, depending on its particular type are abundant carbon precursor. However, previous studies have neglected the possibility of soil modification for CO 2 adsorption. In this study, a natural soil, peat soil was used to prepare dried, carbonised, and alkaline-modified soils. Through nitrogen adsorption-desorption analysis, the porosity of the alkaline modified soil has higher BET surface area and total pore volume of 72.08 m 2/g and 0.11 cm 3/g respectively. Furthermore, the functional groups of OH, C=O, and S=O presence in the adsorbents which were determined by FTIR also capable to assist the adsorption of CO 2. Hence, the performance of the soil after alkaline modification increased by 85% compared to the non-modified soil where the adsorbent recorded an adsorption capacity of 11.70 mg/g. Moreover, the isotherms and kinetics fitting suggest that the adsorption of CO 2 onto the adsorbents was governed by physisorption. In conclusion, modified soils showed better performance for CO 2 adsorption. Thus, further investigations such as optimisation of the modification process or amine functionalisation are anticipated in development of soil-based adsorbents.

Influence of alkaline modification on selected properties of banana fiber paperbricks

In a bid to develop paper bricks as alternative masonry units, unmodified banana fibers (UMBF) and alkaline (1 Molar aqueous sodium hydroxide) modified banana fibers (AMBF), fine sand, and ordinary Portland cement were blended with waste paper pulp. The fibers were introduced in varying proportions of 0, 0.5, 1.0 1.5, 2.0, and 2.5 wt% (by weight of the pulp) and curing was done for 28 and 56 days. Properties such as water and moisture absorption, compressive, flexural, and splitting tensile strengths, thermal conductivity, and specific heat capacity were appraised. The outcome of the examinations carried out revealed that water absorption rose with fiber loading while AMBF reinforced samples absorbed lesser water volume than UMBF reinforced samples; a feat occasioned by alkaline treatment of banana fiber. Moisture absorption increased with paper bricks doped with UMBF, while in the case of AMBF-paper bricks, property value was noted to depreciate with increment in AMBF proportion. Fiber loading resulted in improvement of compressive, flexural, and splitting tensile strengths and it was noted that AMBF reinforced samples performed better. The result of the thermal test showed that incorporation of UMBF led to depreciation in thermal conductivity while AMBF infusion in the bricks initiated increment in value. Opposite behaviour was observed for specific heat capacity as UMBF enhanced heat capacity while AMBF led to depreciation. Experimental trend analysis carried out indicates that curing length and alkaline modification of fiber were effective in maximizing the properties of paperbricks for masonry construction.

Alkaline modification of the acid residue of incinerated sewage sludge ash after phosphorus recovery for heavy metal removal from aqueous solutions

Enriched in phosphorus, sewage sludge ash has been extensively studied and applied as a secondary source for phosphorus recovery. Wet extraction, especially acid washing, is one of the most feasible methods to recover phosphorus from the ash due to its ease of operation, high efficiency and low cost. However, the management of the resultant acid residue was seldom addressed. In this study, special focus was paid to the reuse and recycling of the acid residue by an alkaline activation method. Its adsorption performance towards four different heavy metals in aqueous solutions was evaluated by batch and fixed-bed column adsorption experiments. The obtained material showed a high BET specific area (98.29 m2/g) and a total pore volume (0.114 cm3/g), and effectively removed Cd(II), Cu(II), Pb(II) and Zn(II) from aqueous solutions with the maximum adsorption capacity of around 26.8, 22.2, 53.3 and 13.5 mg/g respectively. It could be loaded in a fixed-bed column to continuously remove heavy metals especially for Pb(II). The proposed method to recycle the acid residue makes the wet extraction methods designing to recover phosphorus from incinerated sewage sludge complete without the generation of waste, which contributes to circular economy and a sustainable future.

Adsorption Capacity of Smectite Clay and Its Thermal and Chemical Modification for Two Anionic Dyes: Comparative Study

The present research evaluates the influence of modification of smectite clay (BC) on its adsorption capacity of anionic dyes from aqueous solutions. Thermal (BC 250), acidic (BC H2SO4), and alkaline (BC NaOH) modification of clay was carried out. The clays were characterized by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Adsorption of dyes was investigated by batch experiments at room temperature (23 ± 2 °C), a wide range of initial dye concentrations (1–1000 mg/dm3), and an adsorbent dose of 50 g. All modifications increased the clay’s adsorption capacity for Reactive Red 198, in the order BC H2SO4 > BC NaOH > BC 250 > BC; it was 10.32, 5.06, 3.32, and 2.92 mg/g, respectively. Acid and thermal modification of the clay increased its adsorption capacity for Acid Red 18, in the series BC H2SO4 > BC 250 > BC > BC NaOH; it was 3.07, 2.66, 2.16, and 1.28 mg/g, respectively. The experimental data were analyzed by Freundlich, Langmuir, Dubinin–Radushkevich, and Sips isotherms, using nonlinear regression. The experimental data best fitted the Sips isotherm. Taking into account the structure of the adsorbent and adsorbates and the results obtained, it can be concluded that the dyes were probably bound through chemisorption, by forming hydrogen bonds between Si–OH and Al–OH groups in the clay and –NH, –NH2, and –OH groups in the dyes. From the results obtained, it can be concluded that smectite clay is a promising material for dye adsorption.

Kinetic evaluation of tobacco stalk waste exposed to alkaline surface treatment under different conditions

Lignocellulosic materials (some natural fibers) have relevant mechanical properties when incorporated in polymeric matrices, being a renewable source to replace synthetic fibers; however, for good adhesion and durability, it is necessary to modify the fibrous surface structure in order to eliminate unwanted compounds. This work aims to evaluate different conditions of alkaline treatment of tobacco stalk waste using 10 and 15 wt% sodium hydroxide (NaOH) during an exposure time of 3 or 5 h. Thermal, chemical, and morphological characterizations as well as kinetic analysis were performed. Through Fourier transform infrared spectroscopy, it was possible to identify the partial removal of compounds such as lignin, hemicellulose, and extractives, increasing the thermal stability, which was proven by thermogravimetric analysis. Furthermore, X-ray diffraction shows a higher crystallinity index from cellulose after the alkaline treatment. Through the kinetic analysis, it is possible to observe that both methods presented similar activation energy values (Ea). In addition, after the alkaline treatment there was a reduction in Ea, the most evident result being observed in the TSW\10\5 sample, which presented an average value of Ea of 223.95 ± 15.79 kJ/mol by the Flynn–Wall–Ozawa method and 218.74 ± 24.69 kJ/mol by the Friedman method. Scanning electron microscopy showed the exposure of the microfibrils and an enhancement of roughness after alkaline treatment. Tobacco stalk wastes has potential application as reinforcing filler in composite materials since surface alkaline modification provides higher fiber/matrix adhesion through the removal of amorphous compounds.

Structure, Dynamic-Mechanical and Acoustic Properties of Oil Palm Trunk Modified by Melamine Formaldehyde

The performance of oil palm trunk wastes from Banjarbaru of South Kalimantan was improved with the help of chemical modification in a two-step treatment. The first was formalization with formaldehyde solution with varying pH, and the second was impregnation with melamine-formaldehyde resin under 5 bar pressure for an hour. In these processes, the samples were cured at 120°C for 10 min and then dried in an oven at (103 ± 2)°C in order to attain a moisture content of less than 6%. These treatments improved the physical properties (density, moisture content, and volume swelling), mechanical resistance, dynamic-mechanical and acoustic performance of the woods. The combination of impregnation and formalization changed the structure and the morphology of the woods such that the surface became flatter and denser. This was confirmed by results from FTIR, SEM, and DMA. Samples with alkaline modification displayed the best results for dimensional stability, storage modulus, and damping factor in varied frequencies. The treatments in this study also heightened acoustic performances as evidenced by the resulting characteristics of sound absorption coefficient and acoustic impedance.

Influence of alkaline modification on different adsorption behavior between ZSM-5 and LSX zeolite for toluene

Abstract Adsorption as an air purification method is widely employed to remove volatile organic compounds with low concentration using zeolites. In this study, ZSM-5 and LSX zeolites modified by alkali metal cations (Li+, Na+ and K+) were used as adsorbents for the abatement of toluene. The adsorption behaviors of toluene onto adsorbents with different pore sizes and cation contents were evaluated systematically based on the experiments of adsorption equilibrium, kinetic diffusion and desorption. Besides, Langmuir and Freundlich model, constant-pattern wave propagation model and Kissinger method were applied to fit with the above experimental data. The adsorption amount followed the sequence of Li-LSX > Na-LSX > K-LSX > Li-ZSM-5 > Na-ZSM-5 > K-ZSM-5 obtained from equilibrium isotherms. LSX zeolites showed twice adsorption capacity on unit volume compared to ZSM-5. The mechanisms of steric hindrances and electrostatic interactions controlling the diffusion rate under high and low concentrations were proposed, respectively. At relatively low loadings of toluene, the diffusion resistances were primarily affected by electrostatic interaction due to preferential adsorption of toluene on cationic sites. While at relatively high loadings, the diffusion resistance was mainly restricted by steric effect because of saturated cationic sites. The strength of adsorbate-adsorbent interactions was assessed by temperature programmed desorption experiments. It showed that both adsorption sites and microporous walls contributed to the desorption energy.

Synthesis of cis-1,3,3,3-tetrafluoropropene by catalytic isomerization of trans-1,3,3,3-tetrafluoropropene over alumina catalysts

Low global warming potential (GWP) refrigerant cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)) is a promising alternative working fluid for high-temperature heat pump designed for heat recovery in the industrial sector. As part of an effort to mass production of HFO-1234ze(Z), the isomerization of trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) to HFO-1234ze(Z) is performed to develop a process with high selectivity and high yield. Herein, we prepared the alumina catalysts via calcination, fluorination, and alkaline modification and tested for the trans-cis isomerization of HFO-1234ze. As a result, the alumina catalyst with appropriate weak Lewis acid sites tended to form HFO-1234ze(Z) with selectivity levels of about 97 %–99 % and no deactivation was observed following time on stream of 200 h. Proposed reaction mechanisms were described to understand the reactions over alumina surface. The present work provides a highly efficient synthetic process for industrial production of HFO-1234ze(Z).

Influence of Wooden Sawdust Treatments on Cu(II) and Zn(II) Removal from Water.

Organic waste materials and semi-products containing cellulose are used as low-cost adsorbents that are able to compete with conventional sorbents. In addition, their capacity to bind heavy metal ions can be intensified by chemical treatments using mineral and organic acids, bases, oxidizing agents, and organic compounds. In this paper, we studied the biosorption capacity of natural and modified wooden sawdust of poplar, cherry, spruce, and hornbeam in order to remove heavy metals from acidic model solutions. The Fourier transform infrared spectroscopy (FTIR) spectra showed changes of the functional groups due to the alkaline modification of sawdust, which manifested in the considerably increased intensity of the hydroxyl peaks. The adsorption isotherm models clearly indicated that the adsorptive behavior of metal ions in treated sawdust satisfied not only the Langmuir model, but also the Freundlich model. The adsorption data obtained for studied sorbents were better fitted by the Langmuir isotherm model for both metals, except for spruce sawdust. Surface complexation and ion exchange are the major mechanisms involved in metal ion removal. We investigated the efficiency of the alkaline modified sawdust for metal removal under various initial concentrations of Cu(II) and Zn(II) from model solutions. The highest adsorption efficiency values (copper 94.3% at pH 6.8 and zinc 98.2% at pH 7.3) were obtained for poplar modified by KOH. For all types of sawdust, we found that the sorption efficiency of modified sorbents was higher in comparison to untreated sawdust. The value of the pH initially increased more in the case of modified sawdust (8.2 for zinc removal with spruce NaOH) and then slowly decreased (7.0 for Zn(II) with spruce NaOH).

Thermal and hydrothermal alkaline modification of kaolin for the adsorptive removal of lead(II) ions from aqueous solution

The properties of Enugu kaolin were modified by thermal and alkaline hydrothermal means. The raw and modified kaolin samples were characterized using Brunauer–Emmett–Teller nitrogen adsorption surface area analysis, X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy and Scanning electron microscopy techniques. The effectiveness of the modified kaolin for the removal of lead(II) ions from aqueous solution was studied and compared to that of the raw kaolin sample. The results showed that the surface area of the modified samples increased from 19.170 m2/g to 247.889 m2/g, 208.745 m2/g and 221.608 m2/g, followed by an increase in the pore volume for the modified samples. However, the modification led to a weak alteration to the kaolin structure. Residual ions detected by atomic absorption spectroscopy showed that the modified kaolin samples have improved removal efficiency for Pb(II) (83%, 88%, 85%) when compared to the raw sample (33%). The adsorption capacities of the raw kaolin and modified kaolin (sample C) were observed to increase with increase in contact time, initial metal ion concentration and adsorbent dose. The adsorption of Pb(II) unto the raw and modified kaolin followed Freundlich (R2 =0.9937) and Langmuir (R2 = 0.9837) adsorption isotherm models respectively. The modified kaolin efficiently eliminated Pb(II) from aqueous solution. Enugu kaolin has the potential to be a catalyst-type material based on the surface analysis and adsorption experiments.

Effect of Alkali-modified Kenaf Fiber Incorporation on the Biodegradability and Hydrolytic Degradability of Used Polyethylene Material

Polyethylene (PE)-based plastic wastes are non-biodegradable and tend to persistently disturb and destroy the environment. The novel approach in this research is incorporation of alkali-modified kenaf fiber into the used PE material aiming at improving its biodegradability and hydrolytic degradation. The alkaline modification of the kenaf fiber was achieved using 5wt. % sodium hydroxide (NaOH) solution as revealed by chemical composition analysis and Fourier Transformed Infrared Spectroscopy of the alkali-treated fiber. Melt-blending approach was employed to fabricate composites using both treated and un-treated kenaf fibers together with the used low density PE, in the form of table water sachets, at various fiber-to-PE loading formulations. Characterizations of these composites were conducted for their biodegradability using Sandy soil. Additional characterizations conducted included hydrolytic degradation and thermogravimetric analysis respectively. In the results obtained for biodegradation and hydrolytic degradation, the alkali treated kenaf fiber-PE composites revealed a more promising performance than its corresponding un-treated kenaf fiber-PE composites. The higher the kenaf fiber the higher the biodegradation and hydrolytic degradation respectively. These composites also showed higher hydrolytic degradation as well as higher thermal stability in comparison to their corresponding un-treated kenaf fiber-PE composites. The findings on Analysis of Variance (ANOVA) revealed that alkali-modified kenaf fiber incorporated PE composites showed a more statistically significant results for biodegradation and hydrolytic degradation particularly between 60 to 90 days retention periods.

Effect of Li, Na and K Modification of Alumina on its Physical and Chemical Properties and Water Adsorption Ability.

The effect of alkali metal (Li, Na, K) incorporation on the morphology and water vapor uptake properties of mesoporous Al2O3 has been studied. The modification of the raw material, pseudoboehmite, represented a mixture of low-temperature phases (γ + η + χ)-Al2O3, and has been done at low-temperature that does not change the phase ratio. A decrease in specific surface values and an average pores size increase were observed as a result of the introduction of metal cations by impregnation and subsequent thermal treatment. The influence of the content of the modifying metal on the adsorption ability of the obtained samples in relation to water vapours has been studied. It has been established that alkaline modification Al2O3 with the lithium cations did not result in adsorption ability improvement, whereas samples that were modified with sodium or potassium in the amount of 1.2 weight % and 2.6 weight %, respectively, possess a higher equilibrium capacity (by ~40%), as compared to that of the initial sample (Al2O3), and a sufficiently high adsorption rate.

Tuning residual metal in partially etched carbide-derived carbons for enhanced acid gas adsorption

Abstract An in-depth study on post-synthetic modification of residual metal in carbide-derived carbons (CDCs) from an Al4C3 starting material has been performed. Ambient temperature high humidity studies reveal the conversion of residual parent nanoparticles to poly(aluminum chloride) (PAC). Alkaline modification was employed resulting in the formation of amorphous Al(OH)3 nanoparticles within 24 h of reaction. After aging for up to 11 days, amorphous nanoparticles convert to well-crystallized α-Al(OH)3 (bayerite). Al4C3-CDCs with amorphous Al(OH)3 display significantly-enhanced interactions with SO2 and CO2 while X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared (ATR-IR) spectroscopy indicated no significant change in the surface chemistry of the carbon. SO2 breakthrough results at 1000 ppm SO2 exhibit uptakes near 2 mmol g−1, displaying viability for these adsorbents in flue gas remediation applications. The results of this work provide detailed modification strategies for tuning the extent and type of residual metal embedded in the final CDC structure, along with further insights into the ramifications of oxygen functionalities and pore size distribution of CDCs for SO2 adsorption.

Insight into the catalytic conversion of palm oil into biodiesel using Na+/K+ trapped muscovite/phillipsite composite as a novel catalyst: Effect of ultrasonic irradiation and mechanism

A novel composite of muscovite/synthetic zeolite (phillipsite) (Mu/Pz) was synthesized in an open system by the alkaline modification at 150 °C under stirring of speed 600 rpm for 22 h. The composite was characterized as a novel, low cost and effective basic catalyst in the transesterification conversion of palm oil into biodiesel. The catalytic properties of Mu/PZ were studied based on several controlling factors by normal stirring and ultrasonic irradiation as mixing techniques. The maximum biodiesel yield obtained by normal stirring is 94% and was accomplished after adjusting the controlling factors at 180 min as conversion interval, 20:1 as the incorporated methanol-to-oil molar ratio, 100 °C as reaction temperature, 5 wt, % as a Mu/Pz loading and 1300 rpm as a stirring speed. The influence of ultrasonic irradiation was addressed within a range from power 20% to power 60% and the best results were achieved using ultrasonic power of 60%. At the same conducting conditions of temperature, Mu/Pz loading, and the incorporated methanol-to-oil ratio, the biodiesel yield attained 97.8% after 90 min by using ultrasonic irradiation as a mixing method at 60% power. The stability study of Mu/Pz catalyst revealed high reusability properties for five cycles using three regeneration solvents of distilled water, methanol and acetone with clear preferences for using the organic solvents. The specifications of the obtained biodiesel samples by both methods match the biodiesel requirements of the STM-D-6571 as well as the EN-14214 international standards.

Alkaline Modification of a Metal–Enzyme–Surfactant Nanocomposite to Enhance the Production of L-α-glycerylphosphorylcholine

Microenvironment modification within nanoconfinement can maximize the catalytic activity of enzymes. Phospholipase A1 (PLA1) has been used as the biocatalyst to produce high value L-α-glycerylphosphorylcholine (L-α-GPC) through hydrolysis of phosphatidylcholine (PC). We successfully developed a simple co-precipitation method to encapsulate PLA1 in a metal–surfactant nanocomposite (MSNC), then modified it using alkalescent 2-Methylimidazole (2-Melm) to promote catalytic efficiency in biphasic systems. The generated 2-Melm@PLA1/MSNC showed higher catalytic activity than PLA1/MSNC and free PLA1. Scanning electron microscopy and transmission electron microscopy showed a typical spherical structure of 2-Melm@PLA1/MSNC at about 50 nm, which was smaller than that of 2-Melm@MSNC. Energy disperse spectroscopy, N2 adsorption isotherms, Fourier transform infrared spectrum, and high-resolution X-ray photoelectron spectroscopy proved that 2-Melm successfully modified PLA1/MSNC. The generated 2-Melm@PLA1/MSNC showed a high catalytic rate per unit enzyme mass of 1.58 μmol mg-1 min-1 for the formation of L-α-GPC. The 2-Melm@PLA1/MSNC also showed high thermal stability, pH stability, and reusability in a water–hexane biphasic system. The integration of alkaline and amphiphilic properties of a nanocomposite encapsulating PLA1 resulted in highly efficient sequenced reactions of acyl migration and enzymatic hydrolysis at the interface of a biphasic system, which cannot be achieved by free enzyme.

Isothermal, kinetic, and thermodynamic studies on copper adsorption on modified styrene acrylonitrile copolymer

The research includes the synthesis of copolymeric material and its chemical modification in order to enhance its adsorptive properties toward copper ions removal. The copolymeric material of acrylonitrile (AN) and styrene (St) was prepared in the ratio of 70:30% V/V, respectively, using 1-propanol as a co-solvent using the precipitation polymerization technique. The prepared copolymeric material undergoes an alkaline modification process using sodium hydroxide. The influence of the modification process variables has been studied on the removal of copper ions where the agitation rate was found to be the most effective parameter in this process. The copolymer chemical structure was investigated through Fourier-transform infrared spectrum, indicating the evaluation of carboxylate groups at 3497 cm−1 after sodium hydroxide treatment. The copolymer thermal stability has been increased by the modification process which was confirmed by thermal characterization. The morphological structure and particle size of the copolymer particles were investigated to be 53.6 nm. The removal process parameters have been studied to show pH variation as a critical parameter in this stage of application. The maximum removal percent was achieved after 90 min to reach 89.6%. The adsorption capacity of the modified (St–AN) copolymer to copper solution was found to be 20 g/L. Thermodynamic, isothermal, and kinetic studies were done where it showed the adsorption process to be spontaneous, thermodynamically favorable, and endothermic in nature.

Influence of alkaline modification on adsorption properties of alumina

The kinetics of water vapor adsorption on alumina adsorbents at a temperature of 25 °C was studied. It was shown that modification by cations of alkali metals (K, Na) of the adsorbent based on alumina allows increasing its efficiency in the process of water vapor adsorption. The mathematical treatment of the experimental data by the dependence of water vapor adsorption on the time with the help of the Linear Driving Force (LDF) model and the dependence of adsorbent’s adsorption capacity on the water vapor concentration (adsorption isotherm) by Dubinin-Astakhov equation was carried out. Constants included in the equations were defined.