Synthesis and characterisation of morin-functionalised silica gel for the enrichment of some precious metal ions

Silica gel was firstly functionalised with aminopropyltrimethoxysilane obtaining the aminopropylsilica gel (APSG). The APSG was reacted subsequently with morin yielding morin-bonded silica gel (morin-APSG). The structure was investigated and confirmed by elemental and thermogravimetric analyses, IR and (13)C NMR spectral studies. Morin-APSG was found to be highly stable in common organic solvents, acidic medium (<2molL(-1) HCl, HNO(3)) or alkaline medium up to pH 8. The separation and preconcentration of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) from aqueous medium using morin-APSG was studied. The optimum pH values for the separation of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) on the sorbent are 5.7, 2.2, 3.7, 3.7 and 6.8, giving rise to separation efficiencies of 43.9, 85.9, 97.7, 60.9 and 91.0%, respectively, where the activity was found to be >90% in the presence of acetate ion. The ion sorption capacity of morin-APSG towards Cu(II) at pH 5.5 was found to be 0.249mmolg(-1) where the sorption capacities of Ag(I) and Pd(II) were 0.087 and 0.121mmolg(-1) and 0.222 and 0.241mmolg(-1) at pH 2.2 and 5.7, respectively. This indicates a 1:1 and 1:2 morin/metal ratios at pH 2.2 and 5.7, respectively. Complete elution of the sorbed metal ions was carried out using 10mL (0.5molL(-1) HCl+0.01molL(-1) thiourea) in case of Au(III), Pd(II), Pt(II) and Rh(III) and 10mL 0.5molL(-1) HNO(3) in case of Ag(I). Morin-APSG was successfully employed in the separation and preconcentration of the investigated precious metal ions from some spiking water samples yielding 100-folds concentration factor. The relative standard deviation (R.S.D.) and the T-test (|t|(1)) were calculated.     

Sensitive detection of trifluoperazine using a poly-ABSA/SWNTs film-modified glassy carbon electrode

A poly-ABSA/SWNTs composite-modified electrode was fabricated by electropolymerizing aminobenzene sulphonic acid (ABSA) on the surface of glassy carbon electrode (GCE) modified with single-wall carbon nanotubes (SWNTs). SWNTs provide a 3D porous and conductive network for the polymer immobilization. The nanocomposite film was characterized by scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS). The results indicated that this composite-modified electrode had strong electrocatalytic activity toward the oxidation of trifluoperazine (TFP). TFP could effectively accumulate on the modified electrode and generate a sensitive anodic peak at 0.72V (versus SCE) in pH 6.1 phosphate buffer solution. Under the selected conditions, the anodic peak current of TFP was linear with its concentration within the range from 1.0x10(-7) to 1.0x10(-5)molL(-1) and 1.0x10(-5) to 1.0x10(-4)molL(-1), and the detection limit was 1.0x10(-9)molL(-1) (S/N=3). This method was successfully applied to the detection of trifluoperazine in drug samples and the recovery was satisfactory. In comparison with the SWNTs/GCE or poly-ABSA/GCE prepared in the similar way, this composite-modified electrode exhibited better catalytic activity.     

Equilibrium and heat of adsorption of diethyl phthalate on heterogeneous adsorbents

The sorption of sodium silicate by synthetic magnetite (Fe3O4) at different pH conditions (pH 7-11) and initial silicate concentrations (1 x 10(-3) and 10 x 10(-3) molL(-1)) was studied using in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The analysis of infrared spectra of sodium silicate in solution as well as adsorbed on magnetite nano-particles clearly showed the evolution of different silicate species depending on pH and silica concentration. The silicate concentration studied (10 x 10(-3) molL(-1)) contained polymeric or condensed silicate species at lower pH as well as monomers at high pH, as evident from infrared spectra. Condensation of monomers resulted in an increased intensity of absorptions in the high frequency part (>1050 cm(-1)) of the spectral region, which contains information about both silicate in solution and sorbed silicate viz. 1300 cm(-1)-850 cm(-1). In the pH range studied, infrared spectra of sorbed silicate and sorbed silicate during desorption both indicated the presence of different types of surface complexes at the magnetite surface. The sorption mechanism proposed is in accordance with a ligand exchange reaction where both monodentate and bidentate complexes could exist at low surface loading level, the relative proportion of the complexes being due to both pH and concentration in solution. Oligomerization occurred on the magnetite surface at higher surface loading.     

Simultaneous determination of dissolved anthracene and pyrene in aqueous solution by synchronous fluorimetry

A synchronous fluorimetry for simultaneous determination of dissolved anthracene and pyrene in aqueous solution has been established. The linear ranges for determination of dissolved anthracene and pyrene were 1.00x10(-8) to 4.50x10(-7)molL(-1) and 5.00x10(-9) to 6.50x10(-7)molL(-1), and the limits of detection (LOD) for anthracene and pyrene were 2.23x10(-9) and 8.24x10(-10)molL(-1) with relative standard deviations (R.S.D.) of 2.90 and 2.34% (n=5), respectively. Satisfactory results were obtained when the established method was used to simultaneously determine anthracene and pyrene in spiked water samples.     

New hydrazine sensors based on electropolymerized meso-tetra(4-sulphonatephenyl)porphyrinate manganese(III)/silver nanomaterial

A new electrocatalytic active porphyrin nanocomposite material was obtained by electropolymerization of meso-tetra(4-sulphonatephenyl)porphyrinate manganese(III) complex (MnTPPS) in alkaline solutions containing sub-micromolar concentrations of silver chloride. The modified glassy carbon electrodes efficiently oxidize hydrazine at 10mV versus Ag/AgCl, dramatically decreasing the overpotential of conventional carbon electrodes. The analytical characteristics of this amperometric sensor coupled with batch injection analysis (BIA) technique were explored. Wide linear dynamic range (2.5x10(-7) to 2.5x10(-4)molL(-1)), good repeatability (R.S.D.=0.84%, n=30) and low detection (3.1x10(-8)molL(-1)) and quantification (1.0x10(-7)molL(-1)) limits, as well as very fast sampling frequency (60 determinations per hour) were achieved.     

Functionalized CdS quantum dots-based luminescence probe for detection of heavy and transition metal ions in aqueous solution

Strong luminescence CdS quantum dots (QDs) have been prepared and modified with l-cysteine by a facile seeds-assistant technique in water. They are water-soluble and highly stable in aqueous solution. CdS QDs evaluated as a luminescence probe for heavy and transition metal (HTM) ions in aqueous solution was systematically studied. Five HTM ions such as silver(I) ion, copper(II) ion, mercury(II) ion, cobalt(II) ion, and nickel(II) ion significantly influence the photophysics of the emission from the functionalized CdS QDs. Experiment results showed that the fluorescence emission from CdS QDs was enhanced significantly by silver ion without any spectral shift, while several other bivalent HTM ions, such as Hg(2+), Cu(2+), Co(2+), and Ni(2+), exhibited effective optical quenching effect on QDs. Moreover, an obvious red-shift of emission band was observed in the quenching of CdS QDs for Hg(2+) and Cu(2+) ions. Under the optimal conditions, the response was linearly proportional to the concentration of Ag(+) ion ranging from 1.25 x 10(-7) to 5.0 x 10(-6)molL(-1) with a detection limit of 2.0 x 10(-8)molL(-1). The concentration dependence of the quenching effect on functionalized QDs for the other four HTM ions could be well described by typical Stern-Volmer equation, with the linear response of CdS QDs emission proportional to the concentration ranging from 1.50 x 10(-8) to 7.50 x 10(-7)molL(-1) for Hg(2+) ion, 3.0 x 10(-7) to 1.0 x 10(-5)molL(-1) for Ni(2+) ion, 4.59 x 10(-8) to 2.295 x 10(-6)molL(-1) for Cu(2+) ion, and 1.20 x 10(-7) to 6.0 x 10(-6)molL(-1) Co(2+) ion, respectively. Based on the distinct optical properties of CdS QDs system with the five HTM ions, and the relatively wide linear range and rapid response to HTM ions, CdS QDs can be developed as a potential identified luminescence probe for familiar HTM ions detection in aqueous solution.     

Utilisation of pH stacking in conjunction with a highly absorbing chromophore, 5-aminofluorescein, to improve the sensitivity of capillary electrophoresis for carbohydrate analysis

This study explores the use of pH stacking in conjunction with 5-aminofluorescein as a derivatization agent for the sensitive analysis of simple sugars such as glucose, lactose and maltotriose by capillary electrophoresis (CE). The derivatization agent was selected on the basis of its extremely high molar absorptivity, its compatibility with a 488nm light-emitting diode (LED) and the fact that it has two ionizable groups making it compatible with on-line stacking using a dynamic pH junction. The influence of both acetic and formic acids at concentrations of 0.19, 0.019 and 0.0019molL(-1) were investigated with regard to both derivatization efficiency and the ability to stack using a dynamic pH junction. Superior sensitivity and resolution was obtained in formic acid over acetic acid. Substantially lower peaks were obtained with 0.19molL(-1) formic acid when compared to 0.019 and 0.0019molL(-1) concentrations, which was confirmed by computer simulation studies to be due to the inadequate movement of the pH boundary for stacking. Further simulation studies combined with experimental data showed the separation with the best resolution and greatest sensitivity when the carbohydrates were derivatized with the 0.095molL(-1) formic acid. Utilisation of stacking via dynamic pH junction mode in conjunction with LED detection enabled efficiencies of 150,000 plates and detection limits in the order of 8.5x10(-8)molL(-1) for simple sugars such as glucose, lactose and maltotriose hydrate. The current system also demonstrates a 515 times improvement in sensitivity when compared to using a normal deuterium lamp, and 16 times improvement over other systems using LEDs.     

Surfaces designed for charge reversal

We have created surfaces which switch from cationic at pH < 3 to anionic at pH > 5, by attaching aminodicarboxylic acid units to silica and gold substrates. Charge reversal was demonstrated by monitoring the adsorption of cationic dyes (methylene blue and a tetracationic porphyrin) and an anionic sulfonated porphyrin, at a range of pH using UV-vis absorption and reflection spectroscopy. The cationic dyes bind under neutral conditions (pH 5-7) and are released at pH 1-4, whereas the anionic dye binds under acidic conditions (pH 1-4) and is released at pH 5-7. Gold surfaces were functionalized with two different amphoteric disulfides with short (CH(2))(2) and long (CH(2))(10)CONH(CH(2))(6) linkers; the longer disulfide gave surfaces exhibiting charge reversal in a narrower pH range. Adsorption is much faster on the functionalized gold (t(1/2) = 62 s) than on functionalized silica (t(1/2) = 6900 s), but the final extents of coverage on both surface are similar, for a given dye at a given pH, with maximal coverages of around 2 molecules nm(-)(2). These charge-reversal processes are reversible and can be repeatedly cycled by changing the pH. We have also created surfaces which undergo irreversible proton-triggered charge switching, using a carbamate-linked thiol carboxylic acid which cleaves in acid. These surfaces are versatile new tools for controlling electrostatic self-assembly at surfaces.     

Green synthesis of loofah-based biosorbent via radiation grafting for effective removal of methylene blue

A new loofah-based biosorbent with high adsorption capacity for cationic dye was synthesized by a one-step co-radiation grafting method. The successful grafting of sodium 4-vinylbenzene sulfonate (SSS) onto loofah sponge (LFs) through electron beam radiation can significantly improve the remove capacity of methylene blue in wastewater. The biosorbent with a 409.67 mg/g of uptake capacity for methylene blue (MB), was higher than most of the loofah based adsorbents reported. FT-IR, elemental analysis, XRD, SEM and TG were used to analyze the changes in the functional group composition, element content, morphology, thermal stability of the obtained biosorbent. The pH, contact time, temperature and the effect of dosage on adsorption were also investigated. The results showed that the adsorption behavior well accorded with the pseudo-second-order kinetic and Langmuir adsorption model, which proved that the adsorption was a single-layered and chemisorption process. The thermodynamic parameters suggested a spontaneous and endothermic process. XPS analysis confirmed a potential adsorption mechanism was based on hydrogen bond interaction, electrostatic interaction and π-π stacking. Additionally, the adsorbent owned outstanding reusability, which could be reused five times with a slight reduction of removal rate. Overall, this research enriches the MB trapping agent and provides a new methods for the reuse of waste natural loofah sponge, and it will be a valuable research with the advantages of low cost and less environmental pollution.     

Cationic Dye Modified Sawdust as Electrode Modifier for Electrochemical Detection of Anions

Because of its chemical properties, sawdust displays poor anionic exchange capacity. Here we demonstrate that sawdust modification with methylene blue (MB) dye represents an interesting and facile alternative to render this natural biomaterial capable to accumulate anionic species. MB adsorption onto sawdust was monitored by cyclic voltammetry and experimental parameters carefully optimized. Under the ideal experimental conditions (composition of accumulation and desorption solution, accumulation and desorption time and the nature of the electrolytic solution), the adsorbed MB showed poor mobility, which results in the absence of the characteristic electrochemical signal of MB. The ability of the material to accumulate anionic species was thus evaluated using Fe(CN)₆^3? as a model anions. The slow Fe(CN)₆^3?/4? system recorded onto the electrode modified by pristine sawdust (P/SFE) become fast and reversible after immobilization of MB onto P/SFE (MB/SFE). Electrochemical impedance spectroscopy confirms this result through the spectacular decrease of charge transfer resistance after MB adsorption (from 83 kΩ on P/SFE to 637 Ω on MB/SFE). MB/SFE was applied to the electroanalysis of nitrites and a sensitivity of 7.4 μA mM^?1 was obtained. Although this sensitivity was less important compared to that obtained on glassy carbon electrode (9.4 μA mM^?1), the dye modified electrode displays by far the best reproducibility even at higher nitrite concentration.     

Modification of microcrystalline cellulose with pyridone derivatives for removal of cationic dyes from aqueous solutions

Microcrystalline cellulose (MCC) was modified with pyridone derivatives such as pyridone diester (PDE) and pyridone diacid (PDA) by using succinic acid anhydride as a linker. The modified MCCs were characterized by the fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric analysis, elemental analysis and solid state ¹³C NMR. The adsorption capacities of the modified MCCs to cationic dyes were examined by using methylene blue (MB) as a model dye. It was found that the kinetic adsorption data followed the pseudo-second-order kinetic model, and the adsorption equilibriums were reached less than 10 min. The isothermal adsorption data were fitted with the Langmuir isotherm model very well, from which the maximum adsorption capacities of the MCCs modified with PDE and PDA were determined to be 101.01 and 142.86 mg/g, respectively. Further investigation showed that the modified MCCs were pH-dependent for adsorption of MB in aqueous solutions. The modified MCCs could be used for removal of MB from an aqueous solution at pH 8, and reused by regeneration in an acidic solution. It was tested that the modified MCCs had a high reusability for removal of MB from aqueous solutions, and still maintained high adsorption capacities even after multiple cycles of desorption–adsorption processes. Hence, the MCCs modified with PDE and PDA could be an effective and efficient approach to removal of cationic dyes from aqueous solutions.     

Brewster angle microscopic study of mixed lipid-protein monolayer at the air-water interface and its application in biosensing

This study investigated lipid-protein LB film formation with Brewster angle microscopy. Our experimental results show that hemoglobin (Hb) molecules can enter the lipid layer and remain for an extended time. We investigated the KCl effect on the LB monolayer of lipid-protein. The lipid-Hb monolayer was transferred from the air-water interface to a QCM gold electrode. UV-vis spectra showed that Hb retained its natural structure in the lipid layer. Cyclic voltammetric (CV) and amperometric systems were applied in this study in order to confirm the remaining bioactivity and sensitivity of Hb to hydrogen peroxide (H(2)O(2)). Lipid-Hb-modified electrodes showed well-defined redox peaks, indicating that the direct electron transfer between Hb and the electrode was enhanced by Hb incorporated in lipid layer. Based on this phenomenon, a novel biosensor for H(2)O(2) was designed. Experimental conditions influencing the biosensor performance such as pH, and potential were optimized and assessed. The levels of the R.S.D.'s (<5%) for the entire analyses reflected the highly reproducible sensor performance. Using optimized conditions the linear range for the detection of H(2)O(2) was observed from 1 x 10(-6) to 1.00 x 10(-4) molL(-1) with a detection limit of 4.00 x 10(-7) molL(-1) (based on the S/N=3).     

Thermodynamics of Chromium(VI) Anionic Species Sorption onto Surfactant-Modified Montmorillonite Clay

Batch sorption experiments performed on Cr(VI) species sorption showed a significantly enhanced removal of inorganic hexavalent chromium anionic species from aqueous solution by montmorillonite clays modified with quaternary amine, hexadecyltrimethylammonium (HDTMA) bromide. Unmodified clay had no affinity for chromium(VI) species. The sorption of Cr(VI) species has been carried out as a function of pH, contact time, adsorbate concentration (4.14x10(-5) to 8.62x10(-3) M), and temperature (5-45 degrees C). The surfactant-modified clay surface was stable when exposed to extremes in pH. The optimum pH for maximum sorption of Cr(VI) species was found to be at pH 1 and was constant between pH 2 and pH 6. The sorption data obtained was well described by DKR and Langmuir sorption isotherms. Sorption energy (E) for (i) surfactant sorption by montmorillonite clay and (ii) sorption of chromium(VI) species by surfactant modified clay have been computed from the DKR equation. Sorption energy evaluated for the sorption of both surfactant and Cr(VI) species showed that an ion-exchange mechanism was operative. The mechanism of retention appears to be replacement of counterion of the surfactant by Cr(VI) anionic species. Adsorbent capacity for the sorption of Cr(VI) species has been evaluated from the Langmuir sorption isotherm data. Thermodynamic parameters (Delta H degrees, Delta S degrees and Delta G degrees ) for surfactant sorption on montmorillonite clay and Cr(VI) sorption by modified clay have been evaluated. The specific rate constant for sorption of Cr(VI) species on modified montmorillonite was rapid during the first 10 min and equilibrium was found to be attained within 30 min. The sorption of Cr(VI) species onto modified montmorillonite clay followed first-order rate kinetics. Copyright 2000 Academic Press.     

Synthesis of NiO coated chitosan-cenosphere buoyant composite for enhanced adsorptive removal of methylene blue

The objective of the present study is to utilize fly ash cenosphere to remove methylene blue (MB) from the water streams. Nickel oxide is a typical semiconductor used as proficient adsorbent material for degradation of dye with environment friendly applications due to its excellent chemical stability and high catalytic activity. The chitosan cenosphere buoyant composite coated with NiO was synthesized with hydrothermal grafting reaction using silane coupling agent and epichlorohydrin as a cross-linking reagent. The batch adsorption experiments were carried out with a cationic dye, methylene blue as a representative organic pollutant to investigate the adsorptive capabilities of the composite as adsorbent. The influence of pH (2-12), initial concentration of dye (50–200 mg/L), temperature (37–47 °C) and contact time (0–24 h) were taken as parameters in the study. On the relative elimination of MB, the effect of time and temperature were investigated. The adsorption kinetics for MB was correlated and found to observe the pseudo-second order kinetic model, whereas the equilibrium adsorption isotherm follows the Langmuir model (R² > 0.99). The results indicate that the floating fly ash cenosphere coated with NiO proved to be more responsive for enhanced degradation of methylene blue.     

Electrochemical behavior and electrocatalytic study of the methylene green coated on modified silica gel

The electrochemical behavior of methylene green (MG) adsorbed on a silica surface modified with niobium oxide (SN) was investigated, using modified carbon paste electrodes. It was also used in an electrocatalytic study of NADH oxidation. The electrode showed a high stability attributed to the presence of SN, which avoids the leaching of the mediator from the electrode surface. The formal potential (E(0')) of the adsorbed MG was -35 mV vs SCE, showing a shift of 30 mV toward more positive potential values, compared to the MG dissolved in aqueous solution. This shift was assigned to the interaction between the basic nitrogen of MG and the acid sites of SN. The variation of the solution pH between 4 and 8 did not affect the stability nor the formal potential. However, for solution pH lower than 4 the formal potential was affected by the acidity of the medium. The electrocatalytic oxidation of NADH at the electrode was investigated. In the solution pH between 5 and 8 the electrocatalytic activity remained almost constant, giving a response signal of 13.3 nA L micromol(-1) cm(-2) and a K(Mapp) of 1.4 x 10(-5) mol L(-1). The electrode gave a linear response range between 5.0 x 10(-4) and 4.0 x 10(-3) mol L(-1) NADH concentration at pH 7.0 at an applied potential of 50 mV vs SCE. Applying a flow injection analysis system, the electrode showed a better analytical performance for NADH detection, presenting a linear response range between 6.0 x 10(-5) and 1.0 x 10(-3) mol L(-1), with an analytical frequency of 30 determinations/h, a detection limit of 8.2 x 10(-6) mol L(-1), and a precision for 25 replicates of 1% expressed as a relative standard deviation.     

Adsorption and kinetic studies of cationic and anionic dyes on pyrophyllite from aqueous solutions

The adsorption of cationic Methylene Blue (MB) and anionic Procion Crimson H-EXL (PC) dyes from aqueous medium on pyrophyllite was studied. Changes in the electrokinetics of pyrophyllite as a function of pH were investigated in the absence and presence of multivalent cations. The results show that pyrophyllite in water exhibits a negative surface charge within the range pH 2-12. Pyrophyllite is found to be a novel adsorbent for versatile removal of cationic and anionic dyes. The negative hydrophilic surface sites of pyrophyllite are responsible for the adsorption of cationic MB molecules. The adsorption of anionic PC dye is possible after a charge reversal by the addition of trivalent cation of Al. Nearly 2 min of contact time are found to be sufficient for the adsorption of both dyes to reach equilibrium. The experimental data follow a Langmuir isotherm with adsorption capacities of 70.42 and 71.43 mg dye per gram of pyrophyllite for MB and PC, respectively. For the adsorption of both MB and PC dyes, the pseudo-second-order chemical reaction kinetics provides the best correlation of the experimental data.     

Fabrication of bulk-modified carbon paste electrode containing alpha-PW12O40(3-) polyanion supported on modified silica gel: Preparation, electrochemistry and electrocatalysis

Alpha-PW(12)O(40)(3-) (PW(12)) supported on the surface of silica gel derivatized by 3-aminopropyl(triethoxy)silane (devoted briefly as SiNH(3)PW(12)) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry. There is an ionic bonding character between PW(12) and the surface amino groups of modified silica, which greatly improves the stability of SiNH(3)PW(12)-modified carbon paste electrode due to insolubility of silica gel in water. The SiNH(3)PW(12) bulk-modified carbon paste electrode not only maintains the electrochemical activity of PW(12), but also exhibits remarkable advantages of renewability, as well as simple preparation and inexpensive material. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of IO(3)(-) and hydrogen peroxide. The SiNH(3)PW(12)-CPE is successfully applied as an electrochemical detector to monitor IO(3)(-) in flow injection analysis (FIA). The catalytic peak current was found to be linear with the IO(3)(-) concentration in the range 5x10(-6) to 1x10(-3)molL(-1). The detection limit of the proposed method was found to be 3.1x10(-6)molL(-1) for IO(3)(-) determination.     

Development of a voltammetric procedure for assay of the antihistamine drug hydroxyzine at a glassy carbon electrode: Quantification and pharmacokinetic studies

An electrochemical study of hydroxyzine at a glassy carbon electrode was carried out in the Britton-Robinson universal buffer of pH 2-11. Hydroxyzine was oxidized in a single two-electron irreversible process controlled mainly by adsorption. A simple, sensitive and time-saving square-wave adsorptive anodic stripping voltammetric procedure has been developed for determination of hydroxyzine in its commercial tablets and human serum without prior extraction. The optimized procedural conditions were: frequency=120Hz, scan increment=10mV, pulse-amplitude=25mV, accumulation potential=-0.3V, accumulation time=90-300s and a Britton-Robinson universal buffer of pH 4 as a supporting electrolyte. Mean recoveries of 100.5+/-0.71 and 98.6+/-1.12% (n=5) were achieved for assay of hydroxyzine in Atarax 10 and 25mg dosage forms, respectively. Limit of detection of 1.5x10(-8)molL(-1) (5.624ngmL(-1)) and limit of quantitation of 5.0x10(-8)molL(-1) (18.746ngmL(-1)) were achieved in human serum with a mean recovery of 98.4+/-1.22%, without prior extraction of the drug. Moreover, the described procedure was applied for evaluating the pharmacokinetic parameters of hydroxyzine in plasma of two healthy volunteers after administration of a single oral dose (Atarax)-25mg).     

Optimization of methylene blue removal from aqueous solutions using activated carbon derived from coffee ground pyrolysis: A response surface methodology (RSM) approach for natural and cost-effective adsorption

This study aimed to examine the impact of operational factors on the adsorption capacity of methylene blue (MB) using a natural and cost-effective adsorbent, activated carbon from coffee grounds (CAP). The three-factor Box-Behnken design of the response surface methodology (RSM) was employed to optimize this economically viable process with maximum efficiency. Through extensive experiments, the factors influencing the adsorption process were identified, their interactions were measured, and a mathematical model was developed. The experiment evaluated the quantity of MB adsorbed by CAP based on pH (2.5–10), initial MB concentration (10–100 mg/L), and CAP adsorbent amount (0.05–0.1 g/L). The results revealed that both concentration and mass significantly influenced the decoloration enhancement. Optimal conditions for achieving a 91 % degradation efficiency were determined as 0.05 g/L adsorbent weight, 100 mg/L dye concentration, and pH 2.5, with a desirability score of approximately 0.986, aligning closely with the predictions of the BBD model. In conclusion, this research addresses a research gap by demonstrating the high effectiveness of the CAP adsorbent in removing dyes from textiles.     

Interaction of colloidal particles of NH(4)(+)-montmorillonite with activated carbon

The interaction between negative colloidal particles of NH(4)(+)-montmorillonite and particles of activated carbon was studied as a function of particle concentration, pH, and time of contact. The results show that carbon particles act as a support/bridge for clay particles, the type of resulting clay/carbon/clay associations depending on the pH and the clay/carbon ratio in the system. The relation between clay and carbon particles can be described by equations of the Langmuir type. For the same carbon particle concentration in the system, the relation varies from 6820 to 36,100 and is dependent on pH. The interaction coefficients at pH 6.5 correspond to reaction of pseudo-first (k(1)=4.14 x 10(-3) to 1.93 x 10(-3) s(-1)) and pseudo-second order (k(2)=9.36 x 10(-14) to 2.47 x 10(-14) cm(3)s(-1)) for different clay/carbon ratios. By using the Dubinin-Radushkevich equation, the interaction energy (+/-22.42, +/-685.0, and +/-14.63 J mol(-1)) was obtained for three different pH values (5, 6.7, and 7.6), demonstrating that the reaction is mainly physical.