Modification and application of multiwalled carbon nanobutes for the separation of arsenic from water

Predmet istraživanja u okviru izrade ove doktorske disertacije bio je razvoj novih, efikasnijih adsorbenata za uklanjanje arsena iz vode. Ispitivanja su uključivala razne vrste modifikacija višeslojnih ugljeničnih nanocevi. U prvom delu ispitivanja je izvršena priprema dva adsorbenta na bazi višeslojnih ugljeničnih nanocevi (MWCNTs), koje su najpre modifikovane oksidacijom (o-MWCNTs), a zatim su aminofunkcionalizovane (e-MWCNTs) i ispitivane kao potencijalni adsorbenti za uklanjanje As(V) iz vode. Takođe, o-MWCNTs i e-MWCNTs su dalje modifikovane u cilju poboljšanja njihovih adsorpcionih karakteristika. Na e-MWCNTs je naneseno gvožđe(III)-oksid u formi goetita na dva načina, vezivanjem Fe3+ jona, kao i vezivanjem Fe2+ jona, koji su zatim oksidovani pomoću KMnO4; na ovaj način dobijeni su e- MWCNTs/Fe 3+ i e-MWCNTs/Fe2+ adsorbenti. o-MWCNTs su naknadno funkcionalizovane sa SOCl2 i aminovane amino-polietilenglikolom (PEG); na taj način je dobijen još jedan novi adsorbent, MWCNTs-PEG. Svi adsorbenti, dobijeni modifikacijom MWCNTs, su detaljno okarakterisani, primenom brojnih instrumentalnih tehnika: FTIR, XRD, BET, SEM, TEM, EDS i ispitivanjem elementarnog sastava, pre i posle adsorpcije, čime su dobijeni podaci značajni za opisivanje mehanizma adsorpcije. U drugom delu istraživanja su ispitivane adsorpcione karakteristike sirovih i modifikovanih MWCNTs, za izdvajanje As(V) i As(III) iz vode, eksperimentima u šaržnom sistemu. Ispitivan je uticaj pH vrednos6 ti rastvora, vremena kontakta, početnih koncentracija arsena i temperature. U okviru ispitivanja adsorpcionih karakteristika sirovih i modifikovanih MWCNTs, kao adsorbenta za As(V) iz vodenog rastvora, eksperimentalno dobijene vrednosti su upoređivani sa šest ravnotežnih i četiri kinetička teorijska modela. Maksimalni adsorpcioni kapaciteti ispitivanih adsorbenata, određeni prema modelu Langmuirove adsorpcione izoterme, su bili u opsegu od 3,55 mg g-1 za MWCNTs bez modifikacije do 23,47 mg g-1 za e-MWCNTs/Fe2+. Na osnovu dobijenih rezultata ispitivanja zaključeno je da je najefikasniji adsorbent e-MWCNTs/Fe2+, koji se može uspešno koristiti za uklanjanje anjonskih vrsta As(V) iz vodenih rastvora, kako pri niskim, tako i pri visokim koncentracijama. Kod ovog adsorbenta su dobijena dobra slaganja između eksperimentalnih rezultata i vrednosti dobijenih modelom, pomoću nekomercijalnog računarskog programa MINTEQ, što omogućava modelovanje sistema i predviđanje rezultata adsorpcije.The research goal of this Ph.D thesis is development of new, more efficient adsorbents for arsenic removal from water. The research was conducted on two modified multiwall carbon nanotubes (MWCNTs). In the first part, two adsorbents based on multiwalled carbon nanotubes (MWCNTs) were synthesized. These adsorbents were prepared by oxidation (o-MWCNTs) following by amination (e- MWCNTs), and examined as potential adsorbents for arsenic removal from water. Moreover, o-MWCNTs and e-MWCNTs were further modified in order to improve their adsorption capacities. Iron(III) oxide, in the form of goethite, was incorporated in the e-MWCNTs surface in two different ways. The first approach was addition of Fe3+ ions, while the second was oxidation of incorporated Fe2+ ions using KMnO4, hence giving both e-MWCNTs/Fe 3+ and e-MWCNTs/Fe2+ adsorbents, respectively. Also, o-MWCNTs were functionalized with SOCl2 and aminated with amino-polyethylene glycol (PEG), making thus one new adsorbent, MWCNTs-PEG. All adsorbents were characterized in detail using numerous instrumental techniques: FTIR, XRD, BET, SEM, TEM, EDS. Elementary composition was determined before and after adsorption. These results gave useful information for characterization of adsorbent before and after adsorption, as well as for the description of adsorption mechanism. In the second part, the adsorption characteristics of raw and modified MWCNTs were determined using the batch system adsorp8 tion experiments. The influence of pH, contact time, initial concentrations and temperature was examined. The kinetic and equilibrium data for the arsenate ion adsorption on synthesized adsorbents were determined by using six equilibrium and four kinetic theoretical models, applying linear and nonlinear fitting methods, in order to evaluate the adsorption mechanism. The maximum adsorption capacities of investigated adsorbents for the removal of arsenate species, determined from the Langmuir adsorption isotherm, were in the range from 3.55 mg g-1 for raw-MWCNTs to 23.47 mg g-1 for e-MWCNTs/Fe2+. Based on presented results, the study showed that the e- MWCNTs/Fe2+ is the most promising adsorbent for the successful removal of As(V) species from aqueous solutions at low and high concentrations. Good agreement of experimental and calculated data was obtained for e-MWCNTs/Fe2+, using non-commercial software MINTEQ. This method enables accurate, swift and efficient modeling system and prediction of adsorption results

Eco-friendly Elderberry based sorbent for removing Pb2+ ions from aqueous solutions

Elderberry (Sambucus nigra) pith was modified with polyethyleneimine (PEI) in order to improve the adsorption properties. Characterization of both dried Sambucus nigra pith (DSNP) and amino modification of elderberry pith with branched PEI (PEI/DSNP) was performed by: Fourier-transform infrared spectroscopy (FTIR), optical microscopy, and porosity determination. The amine and ester number, as well as acid value, were determined on DSNP and PEI/DSNP samples using standard volumetric methods. The samples were used as adsorbents for Pb2+ ions from an aqueous solution in a batch system. The obtained results were fitted using suitable equilibrium isotherm and kinetic models. The maximum adsorption capacity for Pb2+ ions on DSNP and aminаted sample, obtained using Langmuir adsorption isotherm at 298 K, are 18.9 and 47.8 mg g-1, respectively. Based on the kinetic studies, the adsorption process follows the pseudo second-order model. Thermodynamic parameters showed that the adsorption process is endothermic and spontaneous. In general, the overall adsorption process was improved by modifying starting material with branched PEI modifier by introducing large numbers of amino functionalities having high affinity to cations

Evaluation of adsorption performance and quantum chemical modeling of pesticides removal using cell-mg hybrid adsorbent

Magnetite (MG) modified cellulose membrane (Cell-MG), obtained by reaction of 3-aminosilane and subsequently with diethylenetriaminepentaacetic acid dianhydride functionalized waste Cell fibers (Cell-NH2 and Cell-DTPA, respectively), and amino-modified diatomite was used for Azoxystrobin and Iprodione removal from water. Cell-MG membrane was structurally and morphologically characterized using FT-IR and FE-SEM techniques. The influences of operational parameters, i.e. pH, contact time, temperature, and the mass of adsorbent on adsorption and kinetics were studied in a batch system. The calculated capacities of 35.32 and 30.16 mg g-1 for Azoxystrobin and Iprodione, respectively, were obtained from non-linear Langmuir model fitting. Weber-Morris model fitting indicates the main contribution of intra-particle diffusion to overall mass transport resistance. Thermodynamic data indicate spontaneous and endothermic adsorption. The reusability of adsorbent and results from wastewater purification showed that Cell-MG could be used as general-purpose adsorbent. The adsorbent/adsorbate surface interaction was considered from the results obtained using density functional theory (DFT) and calculation of molecular electrostatic potential (MEP). Thus, a better understanding of the relation between the adsorption performances and contribution of non-specific and specific interactions to adsorption performances and design of novel adsorbent with improved properties was deduced

Removal of the As(V) and Cr(VI) from the Water Using Magnetite/3D-Printed Wollastonite Hybrid Adsorbent

In this study, the structure, morphology and composition of the synthesized magnetite/3D-printed wollastonite (3D_W/M) composite were characterized, and its adsorption performance with respect to As(V) and Cr(VI) were studied. Magnetite (MG) modified 3D printed wollastonite was obtained by two step procedure: modification of 3D_W with 3-aminoproylsilane (APTES) followed by controlled magnetite (MG) deposition to obtain 3D_W/M adsorbent. The structure/properties of 3D_W/M were confirmed by applying FTIR, XRD, TGD/DTA, and SEM analysis. The adsorption properties of hybrid adsorbents were carried out for As(V) and Cr(VI) removal-one relative to the initial pH value, the adsorbent mass, the temperature, and the adsorption time. Time-dependent adsorption study was best described by pseudo-second order equation, while Weber Morris analysis showed that intraparticle diffusion controled diffusional transport. Similar activation energy, 17.44 and 14.49 kJ•mol-1 for adsorption As(V) and Cr(VI) on 3D_W/M, respectively, indicated main contribution of physical adsorption. Determination of adsorption parameters was performed by applying different adsorption isotherm models, and the best fit was obtained using Freundlich model. The adsorption capacity of 24.16 and 29.6 mg g-1 for As(V) and Cr(VI) at 2o C, Co = 5.5 and 5.3 mg L-1, respectively, were obtained. Thermodynamic study indicated favourable process at a higher temperature. Preliminary fixed-bed column study and results fitting with Bohart-Adams, Yoon-Nelson, Thomas, and Modified dose-response model showed good agreement with results from the batch study

Optimization of arsenite adsorption on hydroxy apatite based adsorbent using the adaptive neuro-fuzzy inference system / Оптимизация адсорбции арсенита на адсорбенте гидроксиапатита с использованием адаптивной нейро-нечеткой инференционной системы / Optimizacija adsorpcije arsenita na adsorbent na bazi hidroksiapatita korišćenjem adaptivnog neuro-fazi sistema

This paper describes an optimization procedure for the adsorption of arsenite ions from wastewater using the Adaptive Neuro-Fuzzy Inference System (ANFIS). The adsorbent is based on hydroxy apatite, a natural material obtained from carp (Cyprinus carpio) scales. The input parameters were the influence of pH, the temperature, the initial concentration and reaction time of arsenite adsorption while the adsorption capacity and the arsenite removal percentage were studied as the output parameters. / В данной статье описана процедура оптимизации адсорбции ионов арсенита из сточных вод с использованием адаптивной нейронечеткой логической системы (ANFIS). В основе адсорбента лежит природный гидроксиапатитный материал, полученный из чешуи карпа (Cyprinus carpio). В качестве параметров ввода использовались влияние pH, температуры, начальной концентрации и времени реакции на адсорбцию арсенита, а в качестве выходных параметров были исследованы адсорбционная емкость и процент удаления арсенита. / U radu se opisuje postupak optimizacije adsorpcije arsenitnih jona iz otpadnih voda korišćenjem adaptivnog neuro-fazi sistema (ANFIS). U osnovi adsorbenta nalazi se prirodni hidroksi-apatitni materijal dobijen iz krljušti šarana (Cyprinus carpio). Kao ulazni parametri korišćeni su uticaj pH, temperature, početne koncentracije i vremena adsorpcije arsenita, a kao izlazni parametri ispitivani su adsorpcioni kapacitet i procenat uklanjanja arsenita

Analysis of 5 non-coding region in hepatitis C virus by single-strand conformation polymorphism and low-stringency single specific primer PCR

Single-strand conformation polymorphism (SSCP) and low-stringency single specific primer (LSSP)-PCR in hepatitis C virus (HCV) genotyping were examined for informativeness and reliability. The analysis of HCV isolates included seven type 1 isolates, two type 2 isolates, and two type 3 isolates. We also analyzed five isolates that presented as mixed infections determined by type-specific PCR. Among mixed isolates, one isolate was 1a/1b and four isolates were 1b/3a. SSCP and LSSP-PCR were applied to the analysis of 5 non-coding region of HCV (-289 to -5) that contains genotype-specific sequences. Direct cycle sequencing of this region determined sequence divergences that define genotype and sequence alterations within the same genotype. Optimized conditions for the SSCP analysis clearly distinguished between genotypes 1, 2 and 3. In addition, the SSCP analysis detected sequence variants within the same genotype. However, the SSCP analysis and DNA sequencing did not confirm the presence of mixed infections. LSSP analysis, not previously employed in HCV genotyping, enabled clear distinction between genotypes 1, 2 and 3, however, this method did not differentiate between sequence variants within a genotype. Importantly, the LSSP profile demonstrated distinction between mixed infection isolates

CERIUM SUPPORTED ON HIGH POROUS CARBON FROM FISH SCALES CARP, AS A NOVEL LOW COST ADSORBENT TO REMOVE AS(V) IONS FROM WATER

A novel, low cost adsorbent, a cerium supported on high porous carbon from fish scales carp (Cyprinus carpio), has been synthesized to remove As(V) ions from water. The synthesis consisted of chemical and thermal treatment for converting the fish scales into the porous carbon decorated by cerium nanoparticles. By changing the reaction conditions, the porosity and the content of the CeO2 nanoparticles may be controlled in synthesized porous carbon. By optimizing the reaction parameters, using the response surface methodology (RSM) where the output is the result of the adsorbent capacity, a highly efficient material (CeO2-HPC) with a capacity of 81.664 mg g-1 (Langmuir isothermal model) was obtained to remove As (V) ions from the drinking water. The adsorption studies were conducted as a function of pH, contact time, mass of adsorbent and temperature. The best sorption of arsenate ions was achieved for pH between 4.0 and 6.0. The adsorption data for arsenate at 25, 35 and 45 °C are fitted to Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Experimental data were used to model adsorption kinetics using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models. The results showed that the adsorption of As(V) ions onto CeO2-HPC followed the pseudo-second-order kinetic model and Freundlich isotherm models. Thermodynamic parameters, including the Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) changes, indicated that the present adsorption process was feasible, spontaneous and endothermic in the temperature range of 25-45 °C

EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES ON REMOVAL OF Cd(II), Pb(II) AND As(V) FROM WASTEWATER USING CARP (CYPRINUS CARPIO) SCALES

Unmodified farming carp (cyprinus carpio) scales were used as a biosorbent for the removal of Cd(II), Pb(II) and As(V) ions from aqueous solutions. The adsorption studies were conducted as a function of pH, contact time and temperature. The best sorption of cadmium, lead and arsenate ions was achieved for pH between 6.0 and 8.0. The adsorption data for cadmium, lead and arsenate at 20, 30 and 40 °C are fitted to Langmuir, Freundlich, Sips, Dubinin-Radushkevich (D-R), Jovanovic, Jovanovic-Freundlich (J-F), Temkin, Toth and Koble-Corrigan (K-C) isotherm models. Experimental data were used to model adsorption kinetics using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models. The results showed that the adsorption of Cd(II), Pb(II) and As(V) ions onto carp scale followed the pseudo-second-order kinetic model. Thermodynamic parameters, including the Gibbs free energy (Δ

Pulverized river shellfish shells as a cheap adsorbent for removing of malathion from water: Examination of the isotherms, kinetics, thermodynamics and optimization of the experimental conditions by the response surface method

Introduction/purpose: In this study, we investigated the possibility of removing the organophosphorus pesticide malathion from water using a new adsorbent based on the biowaste of river shell shards from the Anodonta Sinadonta woodiane family, a material that accumulates in large quantities as waste on the banks of large rivers. Two adsorbents were tested - mechanically comminuted river shells (MRM) and mechanosynthetic hydroxyapatite from comminuted river shells (RMHAp). Methods: The obtained adsorbents were characterized and tested for the removal of the organophosphorus pesticide malathion from water. In order to predict the optimal adsorption conditions using the Response Surface Method (RSM), the authors investigated the influence of variable factors (adsorption conditions), pH values, adsorbent doses, contact times, and temperatures on the adsorbent capacity. Results: The best adsorption of malathion was achieved at mean pH values between 6.0 and 7.0. The adsorption data for malathion at 25, 35, and 45 °C were compared using the Langmuir, Freundlich, DubininRadushkevich (DR), and Temkin isothermal models, as well as pseudofirst order, pseudo-second order and Elovic kinetic models for modeling adsorption kinetics. The maximum Langmuir adsorption capacity for MRM and RMHAp at 25 °C was 46,462 mg g-1 and 78,311 mg g-1 , respectively. Conclusion: The results have showed that malathion adsorption on both adsorbents follows the pseudo-second kinetic model and the Freundlich isothermal model. The thermodynamic parameters indicate the endothermic, feasible, and spontaneous nature of the adsorption process

Batch and column adsorption of cations, oxyanions and dyes on a magnetite modified cellulose-based membrane

An optimized method is presented to make magnetite (MG) modified cellulose membrane (Cell-MG) from 3-aminopropyltriethoxysilane and diethylenetriaminepentaacetic acid dianhydride functionalized waste cell fibers; (Cell-NH(2)and Cell-DTPA), and amino-modified diatomite. Functionalized Cell-NH2, Cell-DTPA fibers, and diatomite were structurally and morphologically characterized using FT-IR, Raman, and FE-SEM analysis. Amino and carboxyl group content was determined via standard volumetric methods. Response surface method was applied to rationalize the number of experiments related to Cell-MG synthesis and heavy metal ions column adsorption experiments. The effects of pH, contact time, temperature, and initial concentration of pollutants on adsorption and kinetics were studied in a batch, while initial concentration and flow rate were studied in a flow system. The calculated capacities of 88.2, 100.7, 95.8 and 78.2 mg g(-1)for Ni2+, Pb2+, Cr(VI) and As(V) ions, respectively, were obtained from Langmuir model fitting. Intra-particle diffusion as a rate-limiting step was evaluated from pseudo-second-order and Weber-Morris model fitting. Thermodynamic parameters indicated spontaneous and low endothermic processes. The results from reusability study, wastewater purification and fixed-bed column study proved the high applicability of Cell-MG. Additionally, high removal capacity of four dyes together with density functional theory and molecular interaction fields, help in the establishment of relation between the adsorption performances and contribution of non-specific and specific interactions at adsorbate/adsorbent interface