Yongjing Wang

Recycling Mg(OH)2 Nanoadsorbent during Treating the Low Concentration of CrVI

Investigations about how to recycle the deactivated nanomaterials are well-needed. This work was designed to explore the recycling strategy of Mg(OH)(2) nanoadsorbent during treating low concentration of Cr(VI) solution as an example. It was demonstrated that a reversible route between Cr-adsorbed nano-Mg(OH)(2) and Cr-desorbed bulk-MgCO(3) · 3H(2)O can be established by using CO(2) as a phase transformation medium. In each adsorption-desorption cycle, Cr(VI) solution with initial concentration of 10 mg · L(-1) could be enriched over 40 times. An aggregation-induced rapid phase transformation mechanism from nano-Mg(OH)(2) to bulk-MgCO(3) · 3H(2)O was discovered, which was one of the critical factors to ensure the disposing efficiency of this environmental-friendly Cr(VI) disposal system. A pilot-scale experiment was conducted with this strategy to deal with 50 L Cr(VI)-containing simulated industrial wastewater. The enrichment of Cr(VI) and the recycle of nano-Mg(OH)(2) can be successfully achieved simultaneously.

Correlation between the Photoluminescence and Oriented Attachment Growth Mechanism of CdS Quantum Dots

Water-soluble mercaptoacetic acid-coated 3.1 nm CdS quantum dots (QDs) with two concentrations were selected for studying the correlation between the photoluminescence and the crystal growth mechanism. By achieving the classic Ostwald ripening mechanism and oriented attachment (OA) growth mechanism, we have shown that the evolution of the emission spectra were obviously different. The change in both the surface and internal defects during OA crystal growth were responsible for the specific variation of the photoluminescence of CdS QDs. Strategies for obtaining QDs with different luminescent properties are suggested.

Influence of lattice integrity and phase composition on the photocatalytic hydrogen production efficiency of ZnS nanomaterials

Ambient S annealing was adopted to regulate the crystallinity of a ZnS microsphere, which resulted in a significant improvement in the photocatalytic hydrogen production activity (PHPA). Moreover, with S ambient treatment, wurtzite ZnS showed better PHPA than sphalerite ZnS, possibly because the inter-polar electric field of the wurtzite phase could promote the separation of photo-excited electron-hole pairs.

Tunable surface charge of ZnS:Cu nano-adsorbent induced the selective preconcentration of cationic dyes from wastewater.

A novel environmentally friendly nano-adsorbent is developed by doping Cu(+) cations into the lattice of ZnS microspheres. The adsorbent shows selective adsorbability for cationic dyes in low concentrations in wastewater. The adsorbed dye could be successfully eluted with alcohol, resulting in a 1000 fold enrichment of the dye solution.

Treatment of nanowaste via fast crystal growth: With recycling of nano-SnO2 from electroplating sludge as a study case

The treatment of industrial sludge containing amorphous/nanophase metal oxides or hydroxides is one of the vital issues in hazardous waste disposal. In this work, we developed a strategy to recycle nano-SnO(2) from tinplate electroplating sludge. It revealed that the major components of this sludge were acid soluble Sn and Fe amorphous phases. By introducing NaOH as a mineralizer, a fast growth of amorphous Sn compound into acid-insoluble SnO(2) nanowires was achieved selectively. Thus, the as-formed nano-SnO(2) could be recycled via dissolving other solid compositions in the sludge by using acid. The role of NaOH on accelerating both the Oriented Attachment (OA) and Ostwald Ripening (OR) growth of SnO(2) was discussed, which was regarded as a critical factor for treating the sludge. A pilot-scale experiment was conducted to treat 2.3 kg original sludge and the recycling of about 90 g nano-SnO(2) was achieved. We anticipate this work can provide a good example for the recycling of valuable metals from industrial sludge containing fine metal oxides or hydroxides.

The “jump of size” phenomenon in aqueous-nanoparticle reaction system: phase transformation from nano-Mg(OH)2 to bulk MgCO3·3H2O

With the existence of CO2 and H2O, an unusual “jump of size” phenomenon from nano-Mg(OH)2 into bulk MgCO3·3H2O was investigated. It was revealed that the fast growth mode undergoes an in situ conversion of aggregated nano-particles to bulk crystal.