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A novel adsorbent was synthesized via modifying silica nanoparticles with 3-Amino-5-mercapto-1,2,4-triazole and was used to selectively adsorb silver ions from aqueous solutions. The adsorbent was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope and Brunauer-Emmett-Teller (BET) surface area analysis. Batch adsorption experiments were carried out to evaluate the adsorption conditions, reusability and selectivity. The results showed that the optimum pH is 5 and the maximum adsorbability was 124.52 mg/g. The adsorption rate was very high and equilibrium was achieved within 20 min. The total adsorption process preferably followed the pseudo-second order kinetics and the Langmuir isotherm model. The sorbent was stable and efficient. After used five times, the adsorbability was 98.72% of the initial adsorbability. Moreover, the adsorbent adsorb selectively Ag+ from coexisting ions in aqueous solution.

A new adsorbent was synthesized via functionalizing nano-silica with 4-(aminomethyl) pyridine for selective recovery of gold. The adsorbent was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and transmission electron microscopy, and BET (surface area and porosimetry analyzer). The results indicated that the maximum adsorption capacity of Au(III) was 55.5 mg/g at pH 4.0 and room temperature. The adsorption reaction was fairly rapid and reached equilibrium within 30 min. The adsorption processes of Au(III) were fitted well to the Langmuir isotherm model and adsorption kinetics of Au(III) followed the pseudo-second-order rate equation. The adsorption mechanism lies on the chelation and ion exchange between gold ions and amines/hydroxyl groups. The adsorbent had good reusability after five cycles. Moreover, 4-(aminomethyl) pyridine-Silica nanoparticles has a good selectivity in the adsorption of Au(III) from the coexisting ions. Therefore, 4-(aminomethyl) pyridine functionalized nano-silica could be of great potential as new adsorbent for the selective recovery of Au(III) from industrial effluents and waste e-products.

A novel adsorbent was fabricated via grafting sulfoethyl groups on silica nanoparticles to achieve selective adsorption of silver ions from aqueous solution. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA) were used to characterize the adsorbent. The influence of pH, initial concentration, adsorption time and interfering metal ions was investigated. The adsorption equilibrium time was about 60 min and the adsorption capacity for silver ion was 21.9 mg g−1 at pH 6. The adsorption isotherms fitted well with the Langmuir isotherm and the obtained kinetic data support a pseudo-second order adsorption behavior for the functionalized silica nanoparticles. The adsorption mechanism is the chelating interaction. The functionalized silica nanoparticle showed good selectivity to adsorb the silver ions from aqueous solution. The adsorbent could be of great potential as a new class of adsorbent for silver ions.

A new adsorbent thiosemicarbazide/nanosilica composite was synthesized via a facile two-step reaction, including the functionalization of silica nanoparticles via amino groups, and crosslinking the thiosemicarbazide with glutaraldehyde onto the amino functionalized silica nanoparticles. The adsorption capability of the adsorbent for Au(III) ions was investigated. Fourier transform infrared, X-ray photoelectron spectroscopy and thermogravimetric analysis were used to characterize the adsorbent. Experimental results indicated that nanocomposites exhibited highly selective and efficient adsorption for Au(III). The equilibrium data fitted well with the Langmuir isotherm and the obtained kinetic data obeyed the pseudo-second-order kinetics model. The maximum adsorption capacity was 4.3 mmol g−1 at pH 2. The adsorbent can still keep high adsorption capability after five recycling rounds. The adsorption mechanisms were proposed as the synergistic effect of ionic interaction and chelation.

We prepared the carboxymethyl-dithiocarbamate-functionalized silica nanoparticle for detecting silver ions in aqueous media. The functionalized silica nanoparticles were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and thermogravimetric analysis. The functionalized silica nanoparticles realize highly sensitive and selective detection for Ag+ in aqueous solution with an apparent color change over a pH range of 4–6 and under interfering ions. The functionalized silica nanoparticles allow fast detection for Ag+ at 90 °C with a low minimum detectable concentration (0.09 mM). And a remarkable color change also occurs in the presence of Ag+ solutions containing EDTA. This developed technique can easy and fast detect silver ions by the naked eye without using any sophisticated instrumentation.

Silica nanoparticles were functionalized by cation (3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride.) The functionalized silica nanoparticles were used to adsorb anionic dye (xylenol orange) from aqueous solution. The functionalized silica nanoparticles were characterized by XPS and FTIR. The effects of pH, initial concentration, contact time and salts were evaluated. Results showed that the functionalized silica nanoparticles effectively adsorbed anionic dyes from water solution. The adsorption kinetics described well by the pseudo-first-order kinetic model. The adsorption isotherms fitted well with the Langmuir isotherm. The results indicated that the controlling mechanism of adsorption processes was electrostatic adsorption. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1070–1077, 2016

We prepared the catechol-functionalized nanosilica for adsorption of germanium (Ge) ions from aqueous media. The functionalized nanosilica was characterized by FTIR, TGA, TEM, BET, and XPS. The influence of pH, Ge initial concentration, and time of the adsorption process was investigated. Under the optimum condition, the maximum adsorption capacity of Ge ions was 0.048 mg m−2 at pH 4.5. The adsorption mechanism is the chelating interaction between hydroxyl and Ge(OH)4. The functionalized nanosilica was able to selectively adsorb Ge ions from tellurium(IV) and boron. Langmuir isotherm was found to better fit the experiment data rather than Freundlich isotherm. The kinetics of the adsorption process of Ge ions on the functionalized nanosilica was investigated using the pseudo-first-order and pseudo-second-order models, and the results indicated that the pseudo-second order equation model provided the best correlation with the experimental results.

Surface modification of the silica nanoparticles was performed using trithiocyanuric acid (TCA-SNPs) so as to enhance the adsorption of Ag+ from aqueous solutions. The surface modification to the adsorbent was characterized by Fourier transform infrared spectroscopy, transmission electron microscope, and X-ray photoelectron spectroscopy. The Ag+ adsorption capacity was found to increase with increase in the solution pH, with the optimal pH being 5.0. The Ag+ adsorption isotherm was generated at 25 °C at the optimal solution pH and the maximum adsorption capacity was found to be 80 mg/g, significantly higher than the adsorption capacity reported for other adsorbents in literature. The increase in adsorption capacity was attributed to the presence of thiol groups on the surface of the modified adsorbents. Additionally, the adsorption kinetics was estimated at 25 °C, which indicated very high rates of adsorption initially, with rapid reduction in rate of adsorption with time. Both adsorption isotherms as well as the adsorption kinetics were modeled with popular models. The adsorption isotherm was found to match with the Langmuir model while the adsorption kinetics was found to match with the pseudo-second-order kinetic model. The adsorption-desorption cycles indicate the TCA-SNPs to be stable adsorption performance and retain high adsorption efficiency ensuring commercial adoption. A relatively low adsorption of other ions such as Mn2+, Cu2+, Ni2+, Co3+ as compared to Ag+ was ensured.

An ultra fast decopperization method from the anode slime has been developed based on the ultrasound-assisted leaching. The effects of parameters such as ultrasound power, leaching time, sulfuric acid concentration and liquid/solid ratio were investigated. Under optimum conditions, the concentration of Cu in residue was only 2.64%. The removal efficiency increases considerably and the decopperization time was significantly shortened comparing with conventional method (>10%, 24 h). Se and Te have not been detected in lixivium, indicating the selective leaching of Cu. In addition, the mineralogical characteristics of the untreated anode slime and the residues after ultrasound-assisted decopperization are investigated. The results revealed that the increasing of decopperization efficiency was attributed to the change of the phase composition and the morphology and size of samples during ultrasound-assisted decopperization.

A new adsorbent was fabricated via grafting polyethyleneimine (PEI) on activated carbon (AC) to remove anionic amaranth from water. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to characterize the grafting process of PEI. The adsorption behavior of the anionic amaranth (AM) on the modified AC is further evaluated by adjusting pH, the modified AC dosage, contact time and the initial AM concentration. AM adsorption was dramatically dependent of solution pH and the optimum pH is 1.08. The adsorption rate was very high within 20 min and equilibrium was achieved at 180 min. The maximum adsorption amount of AM on the modified AC is 72.68 mg/g at pH 1.08. Compared with the unmodified AC, the adsorption efficiency on the modified AC was dramatically increased from 29.9 to 97%. An electrostatic interaction mechanism was proposed in the acidic solution. The adsorption isotherms were consistent with the Langmuir model and the obtained kinetic data were in accordance with a pseudo-second order adsorption behavior for the modified AC.