Removal of uranium (VI) from water by the action of microwave-rapid green synthesized carbon quantum dots from starch-water system and supported onto polymeric matrix.

Carbon quantum dots (CQDs) are a new class of carbon nanoparticles with superior advantages as small particle size, excellent biocompatibility and low toxicity which advance their recent applications in biotechnology, bioimaging and biosensing. The use of free CQDs in water treatment is greatly rendered by their high solubility in water. Therefore, this work is aimed to rapidly synthesize CQDs in only 10 min via microwave irradiation pyrolysis of starch-water system. The maximum fluorescence emission of CQDs was detected at 526 nm throughout the excitation wavelength (390 nm). The CQDs have been targeted to occupy the surface and pores of a polymeric material based on poly(anthranilic acid-formaldehyde-phthalic acid) (PAFP) to produce a novel CQDs@PAFP nanobiosorbent. The surface area of CQDs@PAFP was detected (28.79 m2 g-1 BET) and the nanoparticle size was confirmed (TEM). The highest removals of U(VI) by CQDs@PAFP nanobiosorbent were 95.5-98.0 % for 30-90 mg L-1. The sorption mechanism was designated to the pseudo-second-order model and closely tailored with Freundlich model. CQDs@PAFP was emerged as an excellent nanobiosorbent for U(VI) removal from wastewater (97.3 %) and sea water (96.0 %). CQDs@PAFP confirmed its excellent reusablity for efficient multi- recovery of U(VI) from different water samples.

A novel nanobiosorbent of functionalized graphene quantum dots from rice husk with barium hydroxide for microwave enhanced removal of lead (II) and lanthanum (III).

In this study, rice husk was used as a sustainable source to synthesize graphene quantum dots (GQDOs) with 2D morphology. Chemical modification of GQDOs with Ba(OH)2 was followed to form a novel GQDOs-Ba nanobiosorbent with an increased number of surface hydroxyl groups. The physicochemical properties of GQDOs and GQDOs-Ba were investigated by FT-IR, SEM, TEM, TGA, and XRD. The adsorption parameters of Pb(II) and La(III) onto GQDOs-Ba were optimized using microwave sorption approach. The maximum capacity reached 3400 µmol g-1 (pH 7), and 1500 µmol g-1 (pH 5) at 15 s for Pb(II) and La(III), respectively. The adsorption isotherm models by GQDOs-Ba fitted well with Langmuir. The pseudo-second order was agreed by Pb(II) and La(III) ions. The thermodynamic studies elucidated that Pb(II) and La(III) adsorption onto GQDOs-Ba followed a spontaneous model. The GQDOs-Ba nanobiosorbent accomplished excellent removal percentages from different water samples containing lead (98.5%-99.8%) and lanthanum (94.6%-96.2%).

Green solid synthesis of polyaniline-silver oxide nanocomposite for the adsorptive removal of ionic divalent species of Zn/Co and their radioactive isotopes 65Zn/ 60Co.

A comparative study between two nanosorbents, nanopolyaniline (NPANI) and nanopolyaniline coated with nanosilver oxide (NPANI-NAg2O) is explored to dispose the divalent species of Zn/Co from water and radioactive isotopes 65Zn/60Co from radioactive wastewater using batch and column techniques. NPANI-NAg2O nanocomposite was synthesized via solid-solid reaction. Characterization was achieved using FT-IR, TGA, XRD, SEM, HR-TEM, and surface area analysis. The images of SEM and HR-TEM confirmed the success of the modification process and the particle size was found in the range 28.78-68.28 nm (NPANI) and 25.74-85.71 nm (NPANI-NAg2O), respectively. Solution pH, contact time, solid dosage, and ionic concentration of the metals were studied as fundamental factors. The obtained results indicated that the optimum conditions to dispose Zn/Co divalent species using NPANI were pH 7 and 30-33 min, while NPANI-NAg2O exhibited the optimum conditions at pH 7 and 20-30 min. The maximum removal capacities were 100.1 and 139.75 mg/g for Zn(II) and 57.93 and 112.1 mg/g for Co(II) using NPANI and NPANI-NAg2O, respectively. Graphical abstract ᅟ.

Solid-solid crosslinking of carboxymethyl cellulose nanolayer on titanium oxide nanoparticles as a novel biocomposite for efficient removal of toxic heavy metals from water.

Nano titanium oxide (Nano-TiO2) was used in this work as a solid support to solid-solid immobilize carboxymethyl cellulose via glutaraldehyde as an efficient cross linking reagent to produce a novel nanosized biocomposite (Nano-TiO2-glu-CMC). The synthesized materials were characterized by FT-IR to confirm crosslinking reaction between the two species as well as by HR-TEM, SEM, TGA and surface area analysis. The particle size was found to correspond to 22.2-44.4nm for Nano-TiO2-glu-CMC. The designed nanosized biocomposite was used and compared with Nano-TiO2 for separation and extraction of heavy metal ions such as Cd(II), Pb(II) and Hg(II) from aqueous solution by using batch experiment and microcolumn technique. The maximum metal sorption capacity values of Cd(II), Pb(II) and Hg(II) were established as 2440µmolg-1 (pH 7), 2880µmolg-1 (pH 6) and 1160µmolg-1 (pH 3), respectively. Optimization of the extraction experiments confirmed the maximum adsorption upon using 0.025g biocomposite dosage and 30min contact time.