Ji Zhi Zhou

Hierarchical Structures of Single-Crystalline Anatase TiO2 Nanosheets Dominated by {001} Facets

mol) were mixed and stirred constantly for 2 min. Thenadditional IBA (30 mL) and HF (10% w/w, 0.4 mL) wereadded to the mixture, which was kept stirring for 2 min. Themixture was heated in a Teflon-lined stainless steel auto-clave (50 mL in volume) and kept in an electric oven at180–2008C for 20 h. The white products were harvested bycentrifugation and washed with ethanol three times. The sur-face fluorine was removed by directly cleaning the productswith NaOH (0.1m) and DI water.

Reduction in the size of layered double hydroxide nanoparticles enhances the efficiency of siRNA delivery.

Small interfering RNAs (siRNAs) are a potentially powerful new class of pharmaceutical drugs for many disease. However, the delivery of unprotected siRNAs is ineffective due to their susceptibility to degradation by ubiquitous nucleases under physiological conditions. Layered double hydroxide nanoparticles (LDHs) have been found to be efficient carriers of anionic drugs and nucleic acids. Our previous research has shown that LDHs (with the Z-average particle size of approximately 110 nm) can mediate siRNA delivery in mammalian cells, resulting in gene silencing. However, short double-stranded nucleic acids are mostly adsorbed onto the external surface and not well protected by LDHs. In order to enhance the intercalation of siRNA into the LDH interlayer and the efficiency of subsequent siRNA delivery, we prepared smaller LDHs (with the Z-average particle size of approximately 45 nm) with an engineered non-aqueous method. We demonstrate here that dsDNA/siRNA is more effectively intercalated into these small LDH nanoparticles, more dsDNA/siRNA is transfected into HEK 293T cells, and more efficient silencing of the target gene is achieved using smaller LDHs. Thus, smaller LDH particles have greater potential as a delivery system for the application of RNA interference.

Synthesis of nanorattles with layered double hydroxide core and mesoporous silica shell as delivery vehicles

This paper describes the controlled synthesis and release properties of MgAl-layered double hydroxide (LDH) mesoporous silica nanorattles. Both LDH and LDH intercalated with fluorescein isothiocyanate (FITC) were coated with mesoporous silica shells to form nanorattles. As-obtained LDH mesoporous silica composites were found to possess the structural features of both LDH and mesoporous silica. The release properties of the nanorattles were evaluated using FITC as the model fluorophore. The LDH-based nanorattles showed controlled release profiles of FITC, which can be attributed to the unique rattle-type structure. The controlled synthesis of LDH mesoporous silica nanorattles thus provides a new opportunity for future development of delivery vehicles.

Effective self-purification of polynary metal electroplating wastewaters through formation of layered double hydroxides.

Heavy metal ions (Ni(2+), Zn(2+), and Cr(3+)) can be effectively removed from real polynary metal ions-bearing electroplating wastewaters by a carbonation process, with ∼99% of metal ions removed in most cases. The synchronous formation of layered double hydroxide (LDH) precipitates containing these metal ions was responsible for the self-purification of wastewaters. The constituents of formed polynary metals-LDHs mainly depended on the Ni(2+):Zn(2+):Cr(3+) molar ratio in wastewaters. LDH was formed at pH of 6.0-8.0 when the Ni(2+)/Zn(2+) molar ratio ≥ 1 where molar fraction of trivalent metal in the wastewaters was 0.2-0.4, otherwise ZnO, hydrozincite, or amorphous precipitate was observed. In the case of LDH formation, the residual concentration of Ni(2+), Zn(2+), and Cr(3+) in the treated wastewaters was very low, about 2-3, ∼2, and ∼1 mg/L, respectively, at 20-80 °C and pH of 6.0-8.0, indicating the effective incorporation of heavy metal ions into the LDH matrix. Furthermore, the obtained LDH materials were used to adsorb azoic dye GR, with the maximum adsorption amount of 129-134 mg/g. We also found that the obtained LDHs catalyzed more than 65% toluene to decompose at 350 °C under ambient pressure. Thus the current research has not only shown effective recovery of heavy metal ions from the electroplating wastewaters in an environmentally friendly process but also demonstrated the potential utilization of recovered materials.

Efficient selective catalytic reduction of NO by novel carbon-doped metal catalysts made from electroplating sludge.

Electroplating sludges, once regarded as industrial wastes, are precious resources of various transition metals. This research has thus investigated the recycling of an electroplating sludge as a novel carbon-doped metal (Fe, Ni, Mg, Cu, and Zn) catalyst, which was different from a traditional carbon-supported metal catalyst, for effective NO selective catalytic reduction (SCR). This catalyst removed >99.7% NO at a temperature as low as 300 °C. It also removed NO steadily (>99%) with a maximum specific accumulative reduced amount (MSARA) of 3.4 mmol/g. Gas species analyses showed that NO removal was accompanied by evolving N2 and CO2. Moreover, in a wide temperature window, the sludge catalyst showed a higher CO2 selectivity (>99%) than an activated carbon-supported metal catalyst. Structure characterizations revealed that carbon-doped metal was transformed to metal oxide in the sludge catalyst after the catalytic test, with most carbon (2.33 wt %) being consumed. These observations suggest that NO removal over the sludge catalyst is a typical SCR where metals/metal oxides act as the catalytic center and carbon as the reducing reagent. Therefore, our report probably provides an opportunity for high value-added utilizations of heavy-metal wastes in mitigating atmospheric pollutions.

Efficient Removal of Sulfur Hexafluoride (SF6) Through Reacting with Recycled Electroplating Sludge

This paper reports that recycled electroplating sludge is able to efficiently remove greenhouse gas sulfur hexafluoride (SF6). The removal process involves various reactions of SF6 with the recycled sludge. Remarkably, the sludge completely removed SF6 at a capacity of 1.10 mmol/g (SF6/sludge) at 600 °C. More importantly, the evolved gases were SO2, SiF4, and a limited amount of HF, with no toxic SOF4, SO2F2, or SF4 being detected. These generated gases can be readily captured and removed by NaOH solution. The reacted solids were further found to be various metal fluorides, thus revealing that SF6 removal takes place by reacting with various metal oxides and silicate in the sludge. Moreover, the kinetic investigation revealed that the SF6 reaction with the sludge is a first-order chemically controlled process. This research thus demonstrates that the waste electroplating sludge can be potentially used as an effective removal agent for one of the notorious greenhouse gases, SF6.

Quick and efficient co-treatment of Zn2+/Ni2+ and CN− via the formation of Ni(CN)42− intercalated larger ZnAl-LDH crystals

The wide use of metal electroplating involving CN(-) necessitates the cost-effective treatment of both CN and metals (Zn, Cu, Ni etc.). In this research, we developed a novel strategy - Ni(2+)-assisted layered double hydroxide (LDH) precipitation - to simultaneously remove aqueous CN and Zn/Ni metals. The strategy is to convert CN(-)/Zn(CN)4(2-) to Ni(CN)4(2-) first, and then to quickly precipitate Ni(CN)4(2-)/CN(-) into LDH crystals. The conversion has been clearly evidenced by the change of CN characteristic FTIR bands of Zn-CN solution before and after adding Ni(NO3)2. The intercalation and efficient removal of CN have also been confirmed through the formation of LDH crystals XRD and SEM. In particular, a set of optimized experimental factors has been obtained by investigating their effects on CN removal efficiency in the simulated tests. Remarkably, over 95% CN were removed with high removal efficiencies of metals. Our results thus suggest that the current strategy is a quick, efficient and promising way to simultaneously treat both Ni and metals/CN rich electroplating wastewaters.

Decomposition of potent greenhouse gas sulfur hexafluoride (SF6) by kirschsteinite-dominant stainless steel slag

In this investigation, kirschsteinite-dominant stainless steel slag (SSS) has been found to decompose sulfur hexafluoride (SF6) with the activity higher than pure metal oxides, such as Fe2O3 and CaO. SSS is mainly made up of CaO·FeO·SiO2(CFS)/MgO·FeO·MnO(RO) phase conglomeration. The SF6 decomposition reaction with SSS at 500-700 °C generated solid MF2/MF3 and gaseous SiF4, SO2/SO3 as well as HF. When 10 wt % of SSS was replaced by Fe2O3 or CaO, the SF6 decomposition amount decreased from 21.0 to 15.2 or 15.0 mg/g at 600 °C. The advantage of SSS over Fe2O3 or CaO in the SF6 decomposition is related to its own special microstructure and composition. The dispersion of each oxide component in SSS reduces the sintering of freshly formed MF2/MF3, which is severe in the case of pure metal oxides and inhibits the continuous reaction of inner components. Moreover, SiO2 in SSS reacts with SF6 and evolves as gaseous SiF4, which leaves SSS with voids and consequently exposes inner oxides for further reactions. In addition, we have found that oxygen significantly inhibited the SF6 decomposition with SSS while H2O did not, which could be explained in terms of reaction pathways. This research thus demonstrates that waste material SSS could be potentially an effective removal reagent of greenhouse gas SF6.

Dual Removal Process of Phosphate on Ca-Layered Double Hydroxide with Substitution of Fe for Al

AbstractUptake of phosphate (PO43−, P) was investigated on two kinds of Ca-layered double hydroxides (LDHs) containing Fe and Al, respectively. The P removal amount was 3.37  mmol/g over Ca-Al-LDH and 2.71  mmol/g over Ca-Fe-LDH. Our results reveal that the removal of P was correlated to the dissolution of LDH as Ca2+ precipitating P to form apatite [Ca5(PO4)3OH] in both cases. It resulted in a constant molar ratio of removed Ca2+ to P(Ca2+/P)=1.8 in the precipitate, which was close to the Ca2+/P ratio in apatite. In particular, the P adsorption on CaxFe(OH)(3+2x) from the hydrolyzed Ca-Fe-LDH was also observed with the corresponding removal amount up to 1.1  mmol/g. This decreased the Ca2+/P ratio in the case of Ca-Fe-LDH from 1.8 to 1.3, when free Ca2+ was unavailable. Consequently, we propose that the dual removal mechanism over Ca-Fe-LDH was attributed to the high aqueous solubility of Fe from the LDH dissolution.