Synthesis and evaluation of a novel cross-linked biochar/ferric chloride hybrid material for integrated coagulation and adsorption of turbidity and humic acid from synthetic wastewater: Implications for sludge valorisation.

The deep removal of organic pollutants is challenging for coagulation technology in drinking water and wastewater treatment plants to satisfy the rising water standards. Iron (III) chloride (FeCl3) is a popular inorganic coagulant; although it has good performance in removing the turbidity (TB) in water at an alkaline medium, it cannot remove dissolved pollutants and natural organic matter such as humic acid water solution. Additionally, its hygroscopic nature complicates determining the optimal dosage for effective coagulation. Biochar (BC), a popular adsorbent with abundant functional groups, porous structure, and relatively high surface area, can adsorb adsorbates from water matrices. Therefore, combining BC with FeCl3 presents a potential solution to address the challenges associated with iron chloride. Consequently, this study focused on preparing and characterizing a novel biochar/ferric chloride-based coagulant (BC-FeCl3) for efficient removal of turbidity (TB) and natural organic matter, specifically humic acid (HA), from synthetic wastewater. The potential solution for the disposal of produced sludge was achieved by its recovering and recycling, then used in adsorption of HA from aqueous solution. The novel coagulant presented high TB and HA removal within 10 min of settling period at pH solution of 7.5. Furthermore, the recovered sludge presented a good performance in the adsorption of HA from aqueous solution. Adsorption isotherm and kinetics studies revealed that the Pseudo-second-order model best described kinetic adsorption, while the Freundlich model dominated the adsorption isotherm.

Exploring the N2 Adsorption and Activation Mechanisms over the 2H/1T Mixed-Phase Ultrathin Mo1-xWxS2 Nanosheets for Boosting N2 Photosynthesis.

Solar-driven conversion of nitrogen (N2) to ammonia (NH3) is highly appealing, yet in its infancy, the low photocatalytic efficiency and unclear adsorption and activation mechanisms of N2 are still issues to be addressed. In this study, ultrathin alloyed Mo1-xWxS2 nanosheets with tunable hexagonal (2H)/trigonal (1T) phase ratios were proposed to boost photoreduction N2 efficiency, while the mechanisms of N2 adsorption and activation were explored simultaneously. The alloyed Mo1-xWxS2 nanosheets for the 1T phase concentration of 33.6% and Mo/W = 0.68:0.32 were proven to reach about 111 µmol gcat-1 h-1 under visible light, which is 3.7 (or 3)-fold higher than that of pristine MoS2 (or WS2). With the aid of density functional theory calculations and in situ N2 adsorption X-ray absorption near-edge fine structure techniques, the adsorption and activation behaviors of N2 over the interface of Mo1-xWxS2 nanosheets were investigated during the N2 reduction process. The results show that the W doping causes a higher electron density state in W 5d orbitals, which can further polarize the adsorbed N2 molecules for adsorption and activation. This work provides a new insight into the adsorption and activation mechanisms for the NH3 synthesis.

Branch number matters: Promoting catalytic reduction of 4-nitrophenol over gold nanostars by raising the number of branches and coating with mesoporous SiO2.

In this study, we demonstrate for the first time that highly branched gold nanostars (AuNSs) and silica-coated AuNSs (AuNSs@mSiO2) could potentially serve as efficient hydrogenation catalysts. The catalytic activity could be promoted by raising the number of tipped-branches of AuNSs, which reveals that the tips play an important role as active sites. The fabricated sharply-pointed AuNSs benefit the electron transfer from BH4 anions to 4-nitrophenol. Coating AuNSs with mesoporous silica (AuNSs@mSiO2) further enhanced the reduction rate and recyclability, and also contributed to reducing the induction period. The AuNSs@mSiO2 (50-100nm in diameter) are large enough to be catalytically inactive, but they consist of sharply-pointed tips with the radius of 2.6-3.6nm, which are rich in coordinately unsaturated sites similar to those of nanoparticles and clusters. Such features in structure and activity would also extend their application range in heterogeneous catalysis.

Gold nanostars: Benzyldimethylammonium chloride-assisted synthesis, plasmon tuning, SERS and catalytic activity.

Fabrication of Au nanostars (AuNSs) can expand the application range of Au nanoparticles because of their high electron density and localized surface plasmon resonance (LSPR) on branches. Exploiting this potential requires further refinement of length of the branches and radius of their tips. To this end, we successfully synthesized AuNSs with uniform and sharply-pointed branches by combining benzyldimethylammonium chloride (BDAC) and cetyltrimethylammonium bromide (CTAB) at low BDAC/CTAB ratios. Once mixed with CTAB, BDAC lowers the critical micelle concentration (CMC) for quick formation of the micelles, which provides favorable growth templates for AuNSs formation. Besides, BDAC increases the concentration of Cl(-), which favors Ag(+) in adsorbing on Au facets. This feature is crucial for the yield boosting and synergic shape control of AuNSs regardless of types of Au seeds used. Use of less amounts of seeds as the center of nucleation benefited sharper and longer growth of the branches. AuNSs exhibited excellent enhancement of surface-enhanced Raman scattering (SERS) intensities as the result of high electron density localized at the tips; however, the enhancement degree varied in accordance with the size of branches. In addition, AuNSs showed high catalytic performance toward the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Efficient catalysis over AuNSs originates from their corners, stepped surfaces and high electron density at the tips.

L-cysteine-modified gold nanostars for SERS-based copper ions detection in aqueous media.

Gold nanostars coated with cysteine (Cys-AuNSs) were successfully synthesized and used in SERS-based copper ions (Cu(2+)) detection in aqueous media. The strong coordination ability of cysteine (Cys) with Cu(2+) and the resulting Cys-AuNSs-Cu complex formation led to AuNSs aggregation and the drastic change in intensity and strength of COOH band spectra. The aggregation of AuNSs yielded distinct SERS signals, which exhibited remarkable sensitivity and selectivity for Cu(2+) over other metal ions. Using this SERS-based sensing method, we have achieved a practical detection limit of 10 µM. Such AuNSs-based detection could provide promising alternative choices for future SERS-active AuNSs application.

Facile synthesis and characterizations of copper-zinc-10,15,20-tetra(4-pyridyl) porphyrin (Cu-ZnTPyP) coordination polymer with hexagonal micro-lump and micro-prism morphologies.

Cu-ZnTPyP coordination polymer with hexagonal micro-lump and micro-prism morphologies has been successfully synthesized through a facile surfactant assisted self-assembly method based on Cu(OAc)2⋅2H2O and Zinc-5,10,15,20-tetra(4-pyridyl) porphyrin (ZnTPyP) in DMF/H2O solvent. The morphologies of three-dimensional micro-prisms and micro-lumps obtained at different concentrations of cetyltrimethylammonium bromide (CTAB) were investigated by scanning electronic microscopy. The compositions of the micro-prisms were studied by energy-dispersive spectra and inductively coupled plasma-atomic emission. X-ray diffraction analysis revealed a circular hexametric cage structure cross-linked by the main Zn-N axial coordination of the pyridyl ligands inside the micro-scale coordination polymers. The UV-Vis diffuse reflection spectroscopy revealed the formation of J-type aggregates in the both microstructures. The formation mechanism of Cu-ZnTPyP coordination polymer structure was investigated by varying CTAB concentration. Their surface photovoltage spectra indicated that the novel hexagonal micro-prism morphology of the coordination polymer displayed enhanced photo response under visible light, which is beneficial for exploiting the practical application of Cu-ZnTPyP compound.