Microwave-enforced green synthesis of novel magnetic nano composite adsorbents based on functionalization of wood sawdust for fast removal of calcium hardness from water samples.

Developing new generation of adsorbents for water treatment to reduce calcium hardness and producing high quality water is important and continuous trend. This manuscript is devoted with this direction. Thus, two novel magnetic nanocomposite adsorbents were synthesized by covalently binding of tartaric acid (TA) and citric acid (CA) to wood sawdust coated magnetic nanoparticles (WSD@Fe3 O4 NPs) using green microwave solvent-less technique. The adsorbents thus prepared WSD@Fe3 O4 NPs-TA and WSD@Fe3 O4 NPs-CA were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Preliminary batch experiments were performed to evaluate percentage of Ca(II) adsorbed by the bare WSD@Fe3 O4 NPs and its functionalized forms by TA and CA, as a function of pH (initial concentration 80 mg/L), indicated 59.5%, 84.70%, and 99.29%, respectively, at pH 7 as optimal value. To attain maximum adsorption capacity, effect of adsorbent dosage and contact time were also optimized for the two modified adsorbents. Accordingly, Ca(II) adsorption capacity was determined to be 18.4 mg/g as exhibited by WSD@Fe3 O4 NPs-TA. However, WSD@Fe3 O4 NPs-CA showed higher capacity value recorded to be 27.2 mg/g. The novel adsorbents were successfully applied for fast reduction of calcium hardness from real water samples, during 15-20 min and via two consecutive in situ batch operations. PRACTITIONER POINTS: This manuscript aims to minimize Ca(II) hardness in aqueous solutions by performing magnetic separation under external magnetic field. WSD was magnetized using Fe3 O4 then modified by using safe organic modifiers using of the benefits of solvent-less microwave radiation technique for adsorbent synthesis and functionalization. Two novel environmentally magnetic nanocomposites WSD@Fe3 O4 NPs-TA and WSD@Fe3 O4 NPs-CA were checked on real water samples.

Adsorptive removal of oil spill from sea water surface using magnetic wood sawdust as a novel nano-composite synthesized via microwave approach.

Water pollution by oil is a serious environmental problem. Developing new generation of benign adsorbents satisfying several criteria required for real practical application is of great need. This work introduces an effort in this direction, by utilizing a facile synthesis of wood sawdust coated magnetite nanoparticles functionalized stearic acid (WSD@Fe3O4NPs/SA) as a novel nano composite along with its precursor WSD@Fe3O4NPs. SA was covalently bonded to the precursor by amide bond formation via the interaction with the silylating agent 3-aminopropyltrimethoxysilane (3-APTS). This mode of binding is more stronger than the conventional ester bond. Fourier transform infrared (FT-IR), X- ray powder diffraction (XRD), Scanning electron microscope (SEM) and Transmittance electron microscope (TEM) were employed for characterization and follow up the synthesis process. Application of the newly synthesized magnetic nano composite adsorbent under optimized parameters of contact time (min) and composite dosage (g) reveal high removal capacity values (g/g) evaluated to be 28.32 g/g, 5 min and 0.1 g for used motor oil removal and 41.22 g/g, 10 min and 0.1 g for crude oil. The high removal efficiency exhibited by WSD@Fe3O4NPs/SA was mainly argued to the long hydrocarbon chain of SA moiety and additional ـــ (CH2)3 ـــ groups incorporated 3-ATPS. Moreover, Analysis of the oil adsorption experimental equilibrium data were well fitted with Freundlish model with correlation coefficients r2 = 0.9788 and 0.9896 for used motor oil and crude oil, respectively. The kinetic data were correlated using two kinetic models and the results were in harmony with pseudo-second order.

New Trend for Acceleration Solid Phase Extraction Process Based on Using Magnetic Nano-adsorbents along with Surface Functionalization through Microwave Assisted Solvent-free Technique.

The use of a microwave assisted solvent-free technique for silica coating of iron magnetic nanoparticles (Fe3O4-MNPs) and their functionalization with three aliphatic diamines: 1,2-ethylenediamine (1,2EDA), 1,5-pentanediamine (1,5PDA) and 1.8-octanediamine (1,8-ODA), were successfully achieved in a very short time. Only 60 min were needed for the nano-adsorbent modification as compared with more than 1000 min using conventional methods under reflux conditions. Their surface characteristics (observed by TEM, XRD and FT-IR), in addition to Cu(II) adsorption capacities (1.805, 1.928 and 2.116 mmol g(-1)) and time of equilibration (5 s) were almost the same. Thus, the time required to accomplish the solid phase extraction process is greatly reduced. On the other hand, the phenomenon of the fast equilibration kinetics was successfully extended on using the functionalized aliphatic diamines magnetic nano-adsorbents as precursors for further microwave treatment. Three selective magnetic nano-adsorbents (Fe3O4-MNPs-SiO2-1,2EDA-3FSA, Fe3O4-MNPs-SiO2-1,5PDA-3FSA and Fe3O4-MNPs-SiO2-1,8ODA-3FSA) were obtained via the reaction with 3-formayl salicylic acid (3FSA) as a selective reagent for Fe(III). At 5 s contact time, they exhibited maximum Fe(III) uptake equal to 4.512, 4.987 and 5.367 mmol g(-1), respectively. Furthermore, modeling of values of metal uptake capacity obtained at different shaking time intervals supports pseudo-second order kinetics.

Effect of aliphatic diamine length functionalized silica coated iron magnetic nanoparticles on metal capacity and speed of Cu(II) uptake from aqueous media.

Three solid phase extractors based on silica coated magnetic nanoparticles (Fe3O4-SiO2) functionalized aliphatic diamines were synthesized. The magnetic core of Fe3O4 was synthesized first by the sol-gel method, then protected by a layer of silica using tetraethylorthosilicate (TEOS) followed by functionalization using three aliphatic diamines: 1,2-ethanediamine (1,2-EDA), 1,5-pentanediamine (1,5-PDA) and 1,8-octanediamine (1,8-ODA). These steps for producing the targeted three adsorbents Fe3O4-SiO2-1,2-EDA, Fe3O4-SiO2-1,5-PDA and Fe3O4-SiO2-1,8-ODA with different amines spacer arm were followed up using Fourier Transform Infrared (FTIR) spectra and scanning electron microscope (SEM). The effect of the spacer arm length of the diamines on selective binding and metal capacity values of Cu(II) ions was studied as a function of the time needed to attain equilibrium under optimized conditions of pH, mass of adsorbent and initial concentration of Cu(II) ions. The order of increasing metal capacity for copper ions using magnetic nano-adsorbents was Fe3O4-SiO2-1,2-EDA < Fe3O4-SiO2-1,5-PDA < Fe3O4-SiO2-1,8-ODA at 5 s equilibrium time.

Novel solid-phase extractor based on functionalization of multi-walled carbon nano tubes with 5-aminosalicylic acid for preconcentration of Pb(II) in water samples prior to determination by ICP-OES.

New solid-phase extractor (MWCNTs-5-ASA) was synthesized via covalent immobilization of 5-aminsalicylic acid onto multi-walled carbon nanotubes (MWCNs). The success of the functionalization process was confirmed using Fourier transform infrared spectroscopy, scanning electron microscope, and surface coverage determination. Batch experiments were conducted as a function of pH to explore MWCNTs-5-ASA efficiency to extract several metal ions viz., Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II). It was found that Pb(II) exhibits the highest extraction percentage with maximum adsorption capacity 32.75 mg g(-1). Its binding performance was well fitted with Langmuir sorption isotherm. On the other hand, the selective separation and preconcentration of trace Pb(II) under dynamic conditions prior to determination by inductively coupled plasma-optical emission spectrometry was investigated under different parameters. These included the rate of flow and volume of sample solution, in addition to the type of the eluate, its volume and concentration. The effect of a variety of foreign ions on the recovery percentage was also evaluated. Trace Pb(II) ions present in 500 mL aqueous solution adjusted to pH 4.0 were retained on 50 mg of MWCNTs-5-ASA and completely eluted using 4.0 mL of 2 M HNO3. The limit of detection and the precision of the method were 0.25 ng mL(-1) and 2.8%, respectively (N = 5). This methodology has been applied for the determination of Pb(II) in water samples with good results.

Novel route for silylation of silica gel and aliphatic amines immobilization based on microwave-assisted solvent free synthesis and their applications for Cu(II) and Fe(III) removal from natural water samples.

This article describes a new route for silica gel silylation and immobilization of aliphatic amines based on microwave-assisted solvent free synthesis to produce new solid phase extractors. The mode of synthesis was optimized under microwave conditions and achieved in a short time without using solvents. The produced phases named: silica gel- monoamine (SG-MA), silica gel- ethylenediamine (SG-EDA) and silica gel- diethylenetriamine (SG-DETA). The selectivity of these phases towards the uptake of Cu(II) and Fe(III) was checked using batch equilibration technique. Microwave radiation power and time of radiation were optimized to obtain the highest metal uptake values. The novel synthesized silica amine phases were characterized using Fourier transform infrared spectra and scanning electron microscope. The effects of different parameters including, hydrogen ion concentration, initial metal ion concentration, mass of the phase and shaking time on binding capacities of both Cu(II) and Fe(III) were explored. Results of sorption isotherms of the phases were better fitted with the Langmuir model (r² ≥ 0.950). In addition, the kinetics data were best fitted with the pseudo-second-order type (r² = 0.999). Application of SG-MA for removal of Cu(II)- and Fe(III)-spiked natural water samples was achieved satisfactorily using batch experiments. The results were found to refer to superior recovery percentages (90.0-97.01 ± 0.010-0.521%) with no significant matrix interferences.

Solid-phase extractors based on 8-aminoquinoline and 2-aminopyridine covalently bonded to silica gel for the selective separation and determination of calcium in natural water and pharmaceutical samples.

Two new silica-gel phases were produced directly via the chemical interaction of 3-chloropropyltrimethoxysilane modified silica gel with 8-aminoquioline, phase I and 2-aminopyridine, phase II under reflux conditions. The selectivity properties exhibited by the phases under investigation for the uptake of Ca(II), Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) were determined at different pH values and shaking times under static conditions. The immobilization process and binding of metal ions to the phases were proved via infrared spectra. The phases showed high performance towards Ca(II) extraction at pH 10.00. The equilibrium data were better fitted with a Langmuir model (r(2) = 0.985). The adsorption kinetics data were best fitted with the pseudo-second-order type. Good validation was obtained on applications of the two phases for the separation and determination of Ca(II) in natural water and pharmaceutical samples with no matrix interferences at pH 10.00 under dynamic conditions prior to determination by AAS.

Selective preconcentration of uranyl ion by silica gel phases modified with chelating compounds as inorganic polymeric ion exchangers.

Four chemically modified chelating silica gel phases (I - IV) with ion exchange groups were tested for their potential capability to selectively bind, extract and preconcentrate uranyl ions (UO(2)(2+)) from different aqueous solutions as well as ore samples. Factors affecting such determination processes were studied and optimized. These included the pH of the contact solution, the mass of the silica gel phase extractant, the stirring time during the application of a static technique and the eluent concentration for desorption of the surface-bound uranyl ion and interfering anions and cations. All these factors were evaluated on the basis of determinations of the distribution coefficient value (K(d)) and the percent recovery (R%). Percent recovery values of 91% for silica phase (II) and 93% for silica phase (IV) were identified in the optimum conditions. The proposed preconcentration method was further applied to uranium ore samples as well as granite samples. The determined percentage and ppm values are in good agreement with the standard assigned ones. The structure of the synthesized silica gel phases (I - IV) and their uranyl bound complexes were identified and characterized by means of infrared analysis, thermal analysis (TGA) and potentiometric titration.

Alumina modified by dimethyl sulfoxide as a new selective solid phase extractor for separation and preconcentration of inorganic mercury(II).

Dimethyl sulfoxide (DMSO) was simply immobilized to neutral alumina via quite strong hydrogen bonding between sulfoxide oxygen and surface alumina hydroxo groups. The produced alumina-modified dimethyl sulfoxide (AMDMSO) solid phase (SP)-extractor experienced high thermal and medium stability. Moreover, the small and compact size of DMSO moiety permit high surface coverage evaluated to be 2.1+/-0.1 mmol g(-1) of alumina. Hg(II) uptake was 1.90 mmol g(-1)(distribution coefficient log K(d)=5.658) at pH 1.0 or 2.0, 1.68 mmol g(-1) (log K(d)=4.067) at pH 3.0 or 4.0 while the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low values 0.513-0.118 mmol g(-1) (log K(d)<3.0) in the pH range 4.0-7.0. A mechanism was suggested to explain the unique uptake of Hg(II) ions by binding as neutral and chloroanionic species predominate at pH values< or =3.0 of a medium rich in chloride ions. A direct and fast batch separation mode was achieved successfully to retain selectively Hg(II) in presence of other eight coexisting metal ions. Thus, Hg(II) was completely retained; Ca(II), Co(II), Ni(II) and Cd(II) were not retained, while Pb(II), Cu(II), Zn(II) and Fe(III) exhibited very low percentage retention evaluated to be 0.42, 0.49, 1.4 and 5.43%, respectively. The utility of the new modified alumina sorbent for concentrating of ultratrace amounts of Hg(II) was performed by percolating 2l of doubly distilled water, drinking tap water, and Nile river water spiked with 10 ng/l over 100mg of the sorbent packed in a minicolumn used as a thin layer enrichment bed prior to the determination by CV-AAS. The high recovery values obtained (98.5+/-0.5, 98.5+/-0.5 and 103.0+/-1.0) based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51-0.97%, N=3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.