Adsorption Of Functional Groups Research Articles

Synthesis and characterization of phenolphthalein derivatives, detailed theoretical DFT computation/molecular simulation, and prevention of AA2024-T3 corrosion in medium 3.5% NaCl

BackgroundAluminum alloy corrosion prevention is a significant problem in the industry. The development of an effective protection strategy is a popular research area. In this work, two organic inhibitors phenolphthalein (P1) and (3-oxo-1, 3-dihydroisobenzofuran-1,1-diyl)bis(4,1-phenylene) bis(4-methyl benzenesulfonate) (P2) were used in 3.5% NaCl medium for alloy AA2024-T3 corrosion mitigation. Corrosion inhibition behavior was investigated by a combination of experimental and theoretical studies. MethodsThe surface morphology of AA2024 -T3 has been identified by scanning electron microscopy coupled with Energy Dispersive X-Ray Spectroscopy (SEM/EDS), and Infrared spectroscopy (FT-IR) confirms the adsorption of functional groups on the surface of the aluminum alloy. Furthermore, the adsorption energies of P1 and P2 on Aluminium (111) interfaces were computed by Molecular Dynamics (MD), and quantum chemical computations (density functional theory, DFT) were chosen for obtaining basic electronic/atomic-scale details about the compound adsorption on target alloy aluminum and their active sites. Significant findingsThe effect of two organic inhibitors phenolphthalein (P1) and (3-oxo-1, 3-dihydroisobenzofuran-1,1-diyl)bis(4,1-phenylene) bis(4-methyl benzenesulfonate) (P2) on the corrosion protection of Aluminium alloy in 3.5% NaCl solution was examined using electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PPD) methods. The Total polarization resistance (RTot) increased, and the corrosion current density declined with the increasing inhibitor concentration. Inhibition efficiency revealed the maximum value of 85% for the P1 and 93% for P2 at 10−4 M, respectively. the two inhibitors were categorized as mixed-type inhibitors since they inhibited both cathodic and anodic corrosion.

Insights on mechanisms of aluminum phytotoxicity mitigation by canola straw biochars from different regions

To better understand the amendment effects and mechanisms of aluminum (Al(III)) phytotoxicity mitigation by different regional crop straw biochars, wheat seedling root elongation trials were conducted. The contributions of liming effect, oxygen-containing surface functional group adsorption, and oxyanions precipitation to Al(III) phytotoxicity mitigation by Ca(OH)2, pristine and ash-free canola straw biochar were evaluated. The results indicated that biochars derived from canola straw collected from four different regions (Yingtan, Xuancheng, Nanjing, and Huaiyin) caused 22–70% wheat seedling root elongation, which might be linked to liming effect. Incorporation of the corresponding ash-free biochars caused 15–30% elongation, which could be attributed to the surface functional group adsorption. About 0–60% of changes could be explained by Al(III) precipitation with inorganic oxyanions. These findings provide new insights into the physicochemical properties, potential applications, efficiencies, and underlying mechanisms of crop straw biochar in alleviating Al(III) phytotoxicity, which is dependent on the cultivation soil, and indicate similar application of crop straw biochar for acidic soil amelioration, contaminated soil remediation, and arable soil improvement.Graphical

H3PO4 activated biochars derived from different agricultural biomasses for the removal of ciprofloxacin from aqueous solution

Biochars were prepared by the pyrolysis of various H3PO4 activated agricultural biomasses at 600 °C and subsequently used as adsorbents for the removal of ciprofloxacin (CIP) from aqueous solution. Peanut shell-based biochar (PSBC), corncob-based biochar (CCBC) and cotton-based biochar (CTBC) had high surface areas (571.0–1006.3 m2/g), well-developed pore structures (mesopores with large pore volumes) and available adsorption functional groups (C=C, C–N and C–O–C). The CIP adsorption onto the biochars was investigated by batch experiments (kinetics, isotherms, thermodynamics, pH, etc.). Thermodynamics calculations showed the spontaneous (ΔGθ<0) and endothermic (ΔHθ>0) nature of the mechanism. In particular, CCBC exhibited high adsorption capacity (120.6 mg/g) of CIP in real lake water and it also had significant removal efficiency of other common pharmaceutical contaminants from real lake environment, and even in a coexisting quintuple system. Finally, multiple interaction mechanisms of CIP adsorption onto aromatized biochar were explored combining characterization analysis and theoretical calculations. Elucidation of the mechanism of CIP adsorption onto biochar provides new insights into the assessment of the removal of pharmaceuticals from the aqueous environment.

Covalent organic framework modified carbon nanotubes for removal of uranium (VI) from mining wastewater

The wastewater containing uranium produced in the mining process is harmful to the environment and life safety due to the inherent biotoxicity and radioactivity of uranium. In this paper, 4,4′-diamino-[1,1′-biphenyl]-3,3′-diol and 2,4,6-triformylphloroglucinol were in situ synthesized β-ketoenamine covalent organic frameworks (COFs) on the surface of carbon nanotubes (CNTs) to obtain a composite of CNT/COF-OH for removal uranium in the rare earth tailings wastewater. Grafting COFs with a large number of specific uranium-binding groups and redox-active sites on the surface of CNTs, CNT/COF-OH can effectively enhance the uranium ion selectivity and adsorption capacity. Furthermore, CNTs have good electron transport capacity and π-conjugation properties, electrons can be effectively transferred from CNTs to COFs, which increases the electron density of the adsorption functional groups, resulting in an increase of the adsorption energy and reductive activity for U (VI), thus improving the removal efficiency. In addition, the skeleton of COFs can be supported by CNTs, thus reducing collapse. Through the synergistic effect of composite, CNT/COF-OH had a good uranium adsorption capacity of 518.2 mg g−1. The adsorption capacity of CNT/COF-OH was increased by 390.7 %, 54.6 %, and 84.5 % compared with those of single CNTs, COF-OH, and mixed CNT + COF-OH, respectively. The selective separation coefficient of CNT/COF-OH was 1.6 times higher than that of COF-OH. The experiment of uranium removal was carried out in the rare earth tailings wastewater using CNT/COF-OH, the removal rate reached 96.7 %. The COFs modified CNTs with synergistic effect have important theoretical and practical significance for the safety problems caused by harmful ions in wastewater.

Ultrasonic treated dried turmeric leaves powder as biosorbent for enhanced removal of lead from aqueous solutions

ABSTRACT The present investigation was targeted to remove toxic heavy metal lead (Pb(II)) from synthetic solution with ultra-sonicated turmeric leaves powder (UTLP) as sorbent. The responsible functional groups for adsorption of Pb(II) onto UTLP were investigated using Fourier Transform Infrared (FTIR) spectroscopy, and the adsorption was confirmed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS) analysis. The Central Composite Design (CCD) method was used to scrutinise the effective parameters. Based on the optimisation results, the maximum % biosorption (97.36) of Pb(II) was attained under optimum conditions of pH: 4.92, biosorbent dosage (BD): 0.44 g and initial solution concentration (ISC): 37.93 mg/L. The experimental findings were fitted with Langmuir and Freundlich and Temkin isotherms. Sequel to isotherm data, the Freundlich model gave good fit with R2 = 0.99 and a maximum adsorption capacity of 36.49 mg/g. The pseudo-second-order model was found to be the most significant for kinetic data analysis. The thermodynamic parameters such as Gibb’s energy change (∆G0 ), enthalpy change (∆H0 ) and entropy change (∆S0 ) were estimated, and it was found that the process was spontaneous and endothermic in nature. Furthermore, the desorption study was conducted with 0.1 N HNO3 to estimate the ease of regeneration behaviour of UTLP. Conclusively, the results revealed that UTLP is prominent and cheap biosorbent for removal of Pb(II) from aqueous medium.

Removal of yttrium from rare-earth wastewater by Serratia marcescens: biosorption optimization and mechanisms studies

The discharge of yttrium containing wastewater is a potential risk to human health. Although biosorption is a promising method to remove yttrium from wastewater, whereas the application of it is limited due to the lack of efficient biosorbents. In this study, the removal of yttrium from wastewater using Serratia marcescens as a biosorbent was conducted. The effects of six parameters including pH (2–5.5), initial yttrium concentration (10–110 mg/L), biosorbent dosage (0.1–0.5 g/L), biosorption time (10–700 min), stirring speed (50–300 rpm) and temperature (20–60 °C) were evaluated. The main parameters were optimized using response surface methodology. The results showed that the adsorption capacity reached 123.65 mg/g at the optimized conditions. The biosorption mechanism was revealed based on a combined analysis using field emission transmission electron microscope-energy dispersion spectrum, Fourier transform infrared spectrophotometer, and X-ray photoelectron spectroscopy. These results revealed that the hydroxyl, carboxyl, and amino groups were the adsorption functional groups for yttrium ions. Biosorption of yttrium by S. marcescens is under the combination of ion exchange, electrostatic attraction and complexation. These findings indicated that S. marcescens can be used as an efficient biosorbent to remove yttrium from wastewater. In addition, its adsorption capacity can be further improved by the enhancement of adsorption functional groups on the surface through chemical modification.

The radiation-induced preparation of ultrasmall gold nanoparticles in Au(III) complexes with units of poly(1-vinyl-1,2,4-triazole) and poly(1-vinyl-1,2,4-triazole) – poly(acrylic acid)

Gold nanoparticles (AuNPs) with average sizes of 1.5 nm and 3 nm and narrow size distribution have been prepared in the irradiated aqueous solutions and suspensions of Au(III)-complexes with units of poly(1-vinyl-1,2,4-triazole) (PVT) and poly(1-vinyl-1,2,4-triazole) – poly(acrylic acid) (PAA) respectively. The formation of AuNPs has been studied using UV-VIS spectroscopy and transmission electron microscopy. The effective stabilization of ultrasmall AuNPs is achieved due to the combination of both electrostatic interaction of polymer units and the specific adsorption of functional groups on the nanoparticle surface. The radiation-chemical approach makes it possible to obtain nanoparticles of a controlled size and containing no impurities of chemical reducing agents.

Covalent adsorption of functional groups on [N]-carbophenes

Starting from the planar molecule 1,3,5-trihydroxybenzene, Du et al reported synthesizing one of a couple of possible 2D materials: graphenylene or 3-carbophene []. 3-carbophene is a member of a novel class of two-dimensional covalent organic framework, [N]-carbophenes (carbophenes). Using a high throughput method, we computed the formation energies and conduction properties of 3-, 4-, 5-, and 6-carbophenes with hydroxyl (OH), carbonyl (CO), nitro (NO2), amine (NH2), carboxyl (COOH) functional groups replacing hydrogen terminating agents. Five hundred and nine structures with randomly picked motifs, with functionalizations from a single functional group per cell to fully functionalized were studied. Our results demonstrate a negatively sloped linear relationship between the degree of functionalization and formation energy when the type of functional group and type of carbophene are held constant. The decrease in formation energy with functionalization makes Du’s synthesis of functionalized 3-carbophene more creditable. The type of carbophene, type of functional group, and the degree of functionalization all play a role in the band structure of the materials. For example, CO functional groups may lead to a mid-gap state pinned to the Fermi level, whereas the other functional groups studied keep the semiconducting nature of pristine carbophene. Thus, because carbonyl functional groups are often present in defected carbon systems, care should be taken to limit the amount of oxygen in carbophene devices where the band gap is important. Thus, this work strengthens the hypothesis of Junkermeier et al's hypothesis that Du et al synthesized 3-carbophene and not graphenylene [].

The Adsorption of Corn Stalk Biochar for Pb and Cd: Preparation, Characterization, and Batch Adsorption Study

Biochar adsorption emerges as a convenient and cheap treatment technology to cope with the metal pollution in wastewater. In this study, a biochar made from corn stalks was prepared and its adsorption characteristics for two heavy metals, Pb and Cd, were investigated by materials characterization and batch experiments. Biochar pyrolyzed from waste corn stalks at 400–600 °C, where biochar prepared at 600 °C (BC600) was used to perform following experiments. In materials characterization, the SEM images were initially used to reveal an obvious porous structure feature of corn stalk biochar, followed by XPS and FT-IR analyses unraveling the effects of functional groups in adsorption, especially for phenol and carboxyl groups. These functional groups provided vital adsorption sites. In batch experiment, batch experiments were conducted under different factors such as pH, temperature, and background ionic strength. The increase of pH and temperature can improve the adsorption capacity, whereas the ionic strength showed negative effects. The adsorption processes of both metals can be interpreted by fitting pseudo-first order model, as indicated in kinetic experiments, and the adsorption isotherm can be well described by the Langmuir model. Overall, this study revealed the characteristics of corn stalk biochar and deciphered the potential adsorption mechanisms.

Efficient photocatalytic degradation of industrial dye using biogenic ZnO NPs

Water pollution reduction and the development of a cost-effective and sustainable platform for its abatement are incessant challenges in today's world. In this regard, the current study describes the formation of zinc oxide nanoparticles (ZnO NPs) via a green/sustainable, cost-effective approach using syzygium cumini leaves and their photocatalytic activity to counter the above-stated problem. The shape, structure, crystallite size, and optical properties of the NPs were all determined using various characterizations FE-SEM, UV–Vis Spectroscopy, XRD, EDX, and FTIR. XRD study revealed that synthesized ZnO NPs are spherical shaped polycrystalline with wurtzite hexagonal structure, with an average crystallite size of 29 nm. The UV–vis absorption spectra at 380 nm revealed the reduction of the precursor into ZnO NPs. FTIR study investigated the surface adsorption of functional groups on NPs. Furthermore, prepared biogenic ZnO NPs showed remarkable photocatalytic degradation potential towards reactive orange-4 (RO-4) dye with dosage variation. 93.9% degradation efficiency was achieved with a 15 mg dosage. Therefore, this research contributes to the development of green/sustainable photocatalysts for environmental remediation.

Design and preparation of functional azo linked polymers for the adsorptive removal of bisphenol A from water: Performance and analysis of the mechanism

In order to effectively remove refractory bisphenol A (BPA) from water, a novel nitrogen doped organic porous functional azo linked polymer (ALP-p) was designed and prepared according to the physicochemical characteristics of propane linked to two phenol hydroxyl groups. This ALP-p was synthesized with 98.5% yield, from pararosaniline and phloroglucinol, via the diazo coupling reaction to produce multiple adsorption functional groups of benzene ring, hydroxyl group and azo group. This functional material showed high adsorption capacity of 357.8 mg/g for 50 mg/L BPA, at 20 °C. The adsorption kinetics and isotherms were described by the pseudo-second-order and Langmuir model, respectively. The major adsorption mechanisms were attributed to the high specific surface area (259.8 m2/g) and pore volume (0.56 cm3/g) related surface adsorption and pore diffusion through porous stereoscopic stacking cavity anchorage. The functional group from the three-dimensional skeleton structures of ALP-p for BPA anchoring endowed chemisorption via π-π interaction between benzene rings and hydrogen-bonding (O–H⋯O, C–H⋯N, C–H⋯O and C–H⋯C) with the hydrogen atom of benzene ring, –OH from BPA and –OH, NN from ALP-p, respectively. The coexisting organic pollutants and alkali environment posed a negative effect on adsorption, while salinity had no significant effect on the process. The adsorption capacity and recovery of ALP-p were >93.5% and 81.6% after five cycles of operation.

Investigating chromium Cr(VI) removal using imidazolium based ionic liquid-chitosan composite adsorptive film

In this study, we prepared a novel promising composite adsorptive film of chitosan modified with 1-butyl-3-methylimidazolium acetate (Chitosan-[BMIM][OAc]) to combine the unique features of ionic liquid into the biosorbent to remove Cr(VI) from contaminated water. The film was characterized through Fourier Transform Infrared Radiation (FT-IR) to ensure proper chemical modification. Batch adsorption studies were systematically conducted to study the effect of parameters like pH, adsorbent dosage, contact time, and the initial concentration of Cr(VI) ions as well as evaluate Cr(VI) removal efficiency. The composite adsorptive film exhibited excellent removal efficiency of almost 87% at optimum pH values (3) and adsorbent dosage (2 g/L). Furthermore, the composite film shows fast kinetics by achieving 87% efficiency within 60 min of contact time. A remarkable adsorption capacity of 125.63 mg/g based on Langmuir isotherm has been demonstrated from the results. After adsorption, FT-IR studies investigation revealed the involvement of OH and NH functional groups in adsorption through electrostatic attraction. The environmentally benign adsorbent synthesized from chitosan biopolymer and [BMIM][OAc] can potentially serve as an excellent adsorbent for Cr(VI) removal from water.

Impact of montmorillonite clay on the homo- and heteroaggregation of titanium dioxide nanoparticles (nTiO2) in synthetic and natural waters

The homoaggregation of titanium dioxide nanoparticles (nTiO2) and their heteroaggregation with ubiquitous natural clay colloids are crucial processes affecting the environmental transport and fate of nTiO2, whereas the latter has received less attention. In this study, the effects of pH, electrolytes, natural organic matter (NOM), and montmorillonite on the homo- and heteroaggregation of nTiO2 were systematically investigated. The isoelectric point of bare nTiO2 was 6.98, whereas TiO2-montmorillonite mixtures remained negative charged due to the reduced particle surface potential by heteroaggregation. Homoaggregation of nTiO2 was mainly affected by anions, whereas heteroaggregation in TiO2-montmorillonite mixtures was mainly affected by cations. Heteroaggregation between nTiO2 and montmorillonite involved the adsorption of CC/CH. Intensive aggregation of nTiO2 was observed with 4 mg/L montmorillonite, whereas with 20 mg/L montmorillonite, the aggregation was significantly inhibited by the over-coverage of montmorillonite. NOM was attached to the surface of nTiO2 with the adsorption of functional groups involving CC/CH and OCO. The addition of NOM effectively reduced the homo- and heteroaggregation of nTiO2, and the stabilizing effect was enhanced with the increased molecular weight and aromatic/aliphatic fraction in NOM. Besides electrostatic repulsion, steric repulsion could also be one of the main stabilization mechanisms of NOM. With Ca2+ in the solutions, the stabilizing effect of NOM was significantly weakened through cation bridging. The addition of montmorillonite could facilitate the aggregation of nTiO2 in the presence of NOM. The homo- and heteroaggregation of nTiO2 were also observed in 7 different types of natural waters. Homoaggregation predominated in waters with high ionic strength and low NOM contents (seawater and groundwater), whereas heteroaggregation predominated in surface freshwater and wastewater systems. The results reflect the instability of nTiO2 in natural aquatic environments and the potential risk they pose to benthic organisms.

Parametric optimization by Taguchi L9 approach towards biodiesel production from restaurant waste oil using Fe-supported anthill catalyst

Restaurant waste oil is easily obtainable from local restaurants, while anthills grow widely in Oro, Nigeria. The anthills were first carbonized, then steam activated to prepare an inert, porous support capable of functional group adsorption. The support was then doped with Fe (II) using FeSO4 and the Fe/A catalyst was used in biodiesel synthesis from the RWO. L9 Taguchi OA was chosen to optimize the transesterification proves parameters comprising of catalyst concentration, methanol to oil ratio, reaction temperature and reaction time. The optimization revealed that methanol concentration does not affect the biodiesel yield significantly, while reaction time has the highest contribution. A biodiesel yield of 99.73 % was attained at 60 °C for 1.5 h with 1.2 % catalyst and 6:1 methanol:oil ratio. GC analysis showed the product to be rich in methyl esters. Fuel characterization tests show that the product has properties exceeding the standards set by ASTM. Kinetic studies show the process adheres to pseudo 1st order kinetics and has high reaction rate and frequency factor (A) with low EA, while the catalyst shows very efficient retention of functional groups, as evident from its reusability up to 7 times. Thus the process is energy and cost efficient, with a potential for commercialization.

In-situ construction of Co(OH)2 nanoparticles decorated urchin-like WO3 for highly efficient degradation of sulfachloropyridazine via peroxymonosulfate activation: Intermediates and DFT calculation

Sulfachloropyridazine (SCP) was commonly used as a broad-spectrum sulfonamide antibiotic and hard to be removed through traditional sewage treatment process. In this study, we developed a simple and controllable strategy to realize in-situ construction of Co(OH)2 nanoparticles decorated urchin-like WO3 (Co(OH)2/WO3), which could efficiently remove SCP through peroxymonosulfate (PMS) activation. Some tiny nanoparticles of Co(OH)2 decorated on the spines/nanorods or surfaces of urchin-like WO3 by transmission electron microscopy (TEM) analysis. The obtained 10 wt% Co(OH)2/WO3 realized completely removal of SCP (degradation efficiency 100%) with a high reaction rate constant (k1) of 0.88 min−1 within 3 min at optimal pH 7. That was because the urchin-like WO3 with numerous adsorption functional groups on its surface (e.g., W = O and –OH bonds) could adsorb the Co2+ easily to form CoOH+, which was perceived the rate-limiting step for PMS activation and generating radicals. Radical quenching experiments indicated that SO4•− played a more significant role than HO• radicals. Density functional theory (DFT) calculation revealed that the atoms of SCP with high Fukui index (f−) were active sites, which preferred to be attacked by the electrophilic SO4•− and HO• radicals. The toxicity of the intermediates by SCP degradation was evaluated by quantitative structure–activity relationship (QSAR) prediction through Toxicity Estimation Software Tool (T.E.S.T.). The possible degradation pathway and catalytic mechanism for SCP removal were proposed. Considering the good catalytic properties of Co(OH)2/WO3-PMS, the material will show great application potential in the removal of emerging contaminants in water.

The role of hydroxyl and carboxyl functional groups in adsorption of copper by carbon nanotube and hybrid graphene–carbon nanotube: insights from molecular dynamic simulation

In the present study, an all-atomic molecular dynamic simulation was used to investigate adsorption of copper ions (Cu (II)) by carbon nanotube and hybrid graphene–carbon nanotube in aqueous solution. In order to study oxygenated functional groups effect including hydroxyl (–OH) and carboxyl (–COOH), these nano-structures were functionalized with OH and COOH groups. To this end, oxygenated functional groups of these Nano-structures including OH and COOH were functionalized with hydroxyl (–OH) and carboxyl (–COOH) groups. The simulation results showed that more Cu (II) ions are adsorbed by hybrid graphene–carbon nanotube than by carbon nanotube alone. Conjugation of graphene and carbon nanotube creates a network of open-pores structures, which increases Cu (II) adsorption sites. According to the results, of the two functional groups, COOH was found to be more effective in adsorbing Cu (II) than OH. Of the nano-structures investigated, hybrid COOH-graphene–carbon nanotube showed the greatest Cu (II) adsorption in aqueous solution.

The role of the oxygen functional groups in adsorption of copper (II) on carbon surface

The effect of carbon surface oxidation on the adsorption of Cu(II) ions from aqueous solution was studied in order to explain the role of the oxygen functional groups in the binding of copper ions. Pristine carbonaceous adsorbent was oxidized to a various extent of oxygen uptake (Fenton-like oxidation < persulphate in H2SO4 < H2O2 in HNO3). Equilibrium adsorption tests were performed in acetate buffer at pH ≈ 5. The results show that the adsorption capacity of pristine adsorbent is expectable low (~0.1 mmol g−1). The oxidized samples adsorb Cu(II) at a considerably higher level of ~1.4 mmol g−1 despite the degree of surface oxidation. Analysis of the surface groups (FTIR, TPD) and surface charge (zeta potential) of used adsorbents and their Cu(II) saturated counterpart lead to the finding that Cu(II) ions are mostly bonded by complexation with the dissociated carboxylic groups (partly formed by anhydrides hydrolysis) probably in the form of Cu(Ac)+ formed in the acetate buffer. The extent of dissociation is given by equilibrium pH during the adsorption and does not depend on the total amount of the surface groups. Thus, the content of active sites and consequently adsorption capacity is independent on the degree of oxidation when pH is kept constant. The results indicate that even moderate oxidation treatment of carbonaceous materials can produce highly effective adsorbents for Cu(II) immobilization.

Spectral Analysis of Drug Loaded Nanoparticles for Drug-Polymer Interactions

PLGA [Poly (lactic-co-glycolic acid)] is a one of the widely used biodegradable polymer. The extensive use of PLGA is due to its biocompatible properties and is also approved by FDA and European Medicine Agency in parenteral drug delivery system. Chitosan (CS) is also an extensively used natural polymer in the field of medicine. It has been well documented as a potential drug carrier due to its biocompatibility. Various reports has also suggested the role of chitosan in formulation of nanoparticles to increase the drug bioavailability and efficacy. The characterization of these systems pose interesting analytical challenges. Fourier Transform Infrared (FTIR) technique helps to analyze the adsorption of functional groups on nanoparticles and also to investigate the drug polymer interactions. X-ray powder diffraction (XRD) analysis helps in detection of crystallinity of drugs and polymers on basis of diffraction patterns. This study investigates the characterizations of methotrexate (MTX) and Fluorouracil (5-FU) loaded nanoparticles of PLGA and chitosan with help of FTIR and XRD techniques.&#x0D; Keywords: PLGA, XRD, MTX, Chitosan, FTIR, 5-FU

Study of the adsorption process of heavy metals cations on Kraft lignin

Kraft lignin is an effective heavy metal adsorbent with potential industrial applications, but the lack of mechanistic understanding of the process is impeding the development of this area, which is provided in this study. It was found the Pb(II) adsorption on Kraft lignin follows an “S” dependency on the environmental pH suggesting the existence of multiple functional groups. Structural characterization revealed adsorption functional groups including phenolic hydroxyl, carboxyl groups and electriferous groups existed in the Kraft lignin sample. Multivalent binding of a bivalent heavy metal cation to more than one functional groups is also expected. By understanding the binding mechanisms, a novel adsorption theory, “1-n cooperative adsorption theory”, was developed to explain this complex interaction. The new theory managed to interpret the experimental data by considering binding mechanisms when an adsorbate can bind with multiple active sites with adsorbent-adsorbent interactions (cooperativity). Kraft lignin exhibit a high adsorption affinity towards Pb(II) (49.8mg/g-lignin at neutral pH) and the process can be easily reversed through pH adjustment, which makes it a promising industrial Pb(II) adsorbent with regeneration abilities. This study provides guidelines for Kraft lignin applications as a heavy metal adsorbent, as well as theoretical backgrounds for other complicated multi-valent surface interactions.

Modified cellulose by polyethyleneimine and ethylenediamine with induced Cu(II) and Pb(II) adsorption potentialities

In order to synthesize adsorbent that can effectively absorb heavy metals in a simple and economical way, this study described the fabrication of adsorbents based on cellulose acetate (CA). CA modified first by polyethyleneimine grafting (CAP) and then by ethylenediamine (CAPE) for enhancing Cu(II) and Pb(II) removal from water. The physico-chemical properties of the modified celluloses were analyzed. It was found that the adsorption functional groups (amino groups) were successfully grafted on cellulose and CAP converted from semi-crystalline to cellulose II after enhancement of ethylenediamine (EDA). Adsorption isotherm results showed that the Cu(II) and Pb(II) removal efficiency by CAPE was significantly higher than that by CAP, and CAP showed a higher adsorption capacity of Cu(II) and Pb(II) than CA, of which the adsorption isotherm modeled with Langmuir isotherms well. The adsorption capacity can significantly be affected by ionic strength and humic acid. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) results demonstrated the complexation between amino groups and Cu(II)/Pb(II) played an important role for adsorption onto CAPE.