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Ethylenediaminetetraacetic acid disodium salt (Na2EDTA) was employed to in-situ modify activated carbon from Typha orientalis during phosphoric acid activation to improve its Ni(II) adsorption capacity. The Ni(II) adsorption capacities of original activated carbon (AC) and Na2EDTA-modified activated carbon (AC-Na2EDTA) were evaluated by batch adsorption experiments. The adsorption isotherms of activated carbons conformed to the Langmuir model. The adsorption equilibrium data showed that the calculated maximum Ni(II) adsorption capacities of the samples enhanced from 15.4 mg/g to 27.9 mg/g after modification with Na2EDTA. The physicochemical properties of AC and AC-Na2EDTA were characterized by N2 adsorption/desorption isotherm, Boehm's titration and X-ray photoelectron spectroscopy (XPS) analysis. No obvious differences of AC and AC-Na2EDTA in nitrogen adsorption/desorption curves and pore size distributions could be observed. However, AC-Na2EDTA (80.9% and 2.10 mmol/g) exhibited a higher (N + O)/C atomic ratio and total functional groups content than AC (26.2% and 1.35 mmol/g). These results suggested that chemisorption is mainly responsible for Ni(II) adsorption on activated carbon. Based on the results of batch adsorption experiments and XPS analysis, Ni(II) cations were mainly bound with the O-containing and N-containing groups through the mechanisms of cation exchange, electrostatic attraction and surface complexation. Desorption experiments showed maximum Ni(II) recovery in HCl solution.

A simple but sensitive system for the detection of DNA using molybdenum disulfide (MoS2) as an additive to the DNA solution is reported. According to the described method, the target DNA can be identified by differential pulse voltammetry (DPV) because single- and double-stranded DNA molecules have different affinities to both the electrochemical indicator used (methylene blue) and MoS2. The MoS2 additive does not require any functionalization to achieve adequate sinking speed, contrary to graphene- and carbon nanotube-based additives. The easy fabrication of the sensitive DNA sensor developed in this study is achieved by simply adding the MoS2 additive into the DNA sample solutions, and does not require any sophisticated processes, such as probe immobilization and chemical modification. The results described in this study pave the way for utilizing semiconducting or insulating two-dimensional materials as additives for simple electrochemical DNA sensors with a great potential for commercial mass production.

The present study investigated fluoride removal by high-gradient superconducting magnetic separation (HGSMS) and paramagnetic adsorbents. FeAlOxHy adsorbents with different Fe/Al molar ratios were synthesized and characterized. The adsorption capacities of FeAlOxHy increased with increasing Al content. The FeAlOxHy were effectively separated in HGSMS, and approximately 87% of the fluoride was removed. Higher magnetic intensity, lower flow rate and finer steel wool are among the advantages of FeAlOxHy separated in HGSMS. The maximum desorption efficiency of fluoride adsorbed by FeAlOxHy was measured as 92.06%. A fluoride concentration time value of 40 was obtained using FeAlOxHy followed by the HGSMS process.

In this work, we synthesize Ag@Au core–shell nanoparticles (NPs) and use them as probes for the colorimetric detection of cyanide in aqueous solution. Ag@Au core–shell NPs before and after cyanide treatment are characterized with UV–vis spectroscopy, transmission electron microscopy and electrospray ionization time-of-flight mass spectrometry. The sensing mechanism is based on the fact that cyanide can successively etch gold shells and silver cores of the bimetallic NPs, leading to color changes from purple to orange, yellow and finally colorless. The decreased absorbance intensity at 520 nm is linear with the concentration of cyanide in the range of 0.4–32 μM with a correlation coefficient of 0.995. The limit of detection is 0.16 μM, which is, to our best knowledge, the lowest among the colorimetric methods. The colorimetric assay exhibits excellent selectivity for cyanide over the other 16 anions tested. The proposed method is used for the analysis of cyanide in drinking water, and the recoveries are in the range of 90.0–116.4% with the relative standard deviations lower than 6.7%. Furthermore, the Ag@Au core–shell NPs are functionalized with polysorbate 40 (PS 40), and the PS 40-Ag@Au core–shell NPs remain stable in the presence of high salt, which makes them feasible for the determination of cyanide in sewage samples with complex matrices.

Scanning electrochemical microscopy(SECM) has made great progress in recent years with respect to both technology and applications. This manuscript is an expansion of the review published in Analytica chimica acta in the year of 2007 by our group. The review briefly presents the principle and instrumentation of SECM. Then we focus on the application of SECM in several areas such as charge transfer, solar cells, imaging, bioanalysis in recent years. SECM can capture real time (electro)chemical information at a micro interface which helps us to explore the microscopic world. SECM is also employed to investigate the complicated electron transfer system and biosamples. Last seven years literature infers SECM is a comprehensive characterization tool when it is combined with other techniques.

Three kinds of modified expanded graphite (EG), impregnated with phosphoric acid (H3PO4) (P-EG), impregnated with glucose (G-EG), and impregnated with H3PO4 and glucose (G-P-EG), were prepared under a low temperature (150 °C). The adsorption capacity of G-P-EG (Qm = 7.016 mg/g) is much higher than original expanded graphite (EG Qm = 0.423 mg/g) and other two kinds of modified expanded graphite (P-EG Qm = 0.770 mg/g; G-EG Qm = 0.507 mg/g). The physicochemical properties of EG and G-P-EG were characterized by N2 adsorption/desorption, Boehm's titration and X-ray photoelectron spectroscopy (XPS). EG exhibited higher values of BET surface area (11.357 m2/g) and total pore volume (0.0303 cm3/g) than that of G-P-EG (4.808 m3/g and 0.0109 cm3/g). However, the results of Bohm's titration and XPS showed that G-P-EG contained more surface oxygen-containing functional groups. The Ni(II) adsorption equilibrium data agreed well with the Langmuir model. And the experimental data of EG and G-P-EG fitted better by pseudo-second order model. Based on the results of batch adsorption experiments and XPS analysis, there were several possible mechanisms for Ni(II) adsorption on the G-P-EG, including chemical adsorption, cation exchange, electrostatic attraction and surface complication.

We report a simple colorimetric assay for Hg2+ measurements using label-free gold nanoparticles (Au NPs, 13.0 ± 1.6 nm) with the aid of thiourea (TU). The addition of TU into Au NPs resulted in aggregation of Au NPs with a red-to-blue color change. While in the presence of Hg2+, it inhibited the aggregation of Au NPs induced by TU, resulting in a reverse color change from blue to purple and finally to wine red. These color variations are dependent on the Hg2+ concentration and can be utilized for the colorimetric sensing of Hg2+. This assay requires only 3 min to reach a naked-eye detection limit of 100 nM, which satisfies the guideline concentration of Hg2+ (250 nM) in industrial water regulated by the EPA. And the concentration of Hg2+ is quantitatively determined using a UV-vis spectrophotometer with a limit of detection (LOD) of 40 nM. The response of the assay caused by Hg2+ (2 μM) was 6.0 to 9.1 times higher than those induced by other metal ions (100 μM), indicating its high specificity towards Hg2+. The assay has been applied for the analysis of Hg2+ in drinking and lake water samples with recoveries in the range of 98.3–120.0%.

The dispersibility is one of the important physical properties of inkjet ink, it plays a crucial role on whether the ink can be sprayed smoothly and whether the nozzle will be clogged by the ink, it is the key performance indicator relating to the dispersion system’s stability and uniformity of pigment particle. The study analyzed and compared the effects of monomer and dispersant on the dispersion of yellow UV-LED inkjet ink. Research shows that the particle size of different yellow color paste grinded by different monomer has difference; the dispersion of color paste of single monomer is better than that of composite monomer; the type and content of the dispersant have different effects on the particle size of yellow color paste, under this experimental condition, when the content of dispersant BYK9077 is 8%, its grind effect is the best; moreover, through the study, the formula of color paste of the yellow UV-LED inkjet ink is optimized and determined.

The present study explored the utilization of wool waste (WW) for preparing activated carbon by muffle furnace (MFAC) and microwave (MAC) heating methods with phosphoric acid activation. MFAC was produced by activating at 550 °C for 40 min in muffle furnace. MAC was prepared with radiation power of 700 W and radiation time of 15 min. The physicochemical properties of the activated carbons were determined by N 2 adsorption/desorption, Boehm's titration, and Fourier-transform infrared spectroscopy (FTIR). The sorption behaviors of the carbons toward Ni(II) were investigated through batch sorption experiments. MAC exhibited slightly larger surface area (519 m 2 /g) than MFAC (472 m 2 /g). However, results from Boehm's titration and FTIR suggested that MFAC contained more surface oxygen-containing functional groups than MAC. Sorption experiments indicated that MFAC presented better performance for Ni(II) sorption (17.87 mg/g) than MAC (6.09 mg/g). The sorption followed well the pseudo-second-order kinetic model and the sorption isotherms simulated well the Freundlich model for both of the carbons. Based on the physicochemical properties of activated carbons and the result of the sorption studies, oxygen-containing functional groups played an important role in the sorption of Ni(II). The likely important mechanisms for Ni(II) sorption onto MFAC and MAC were cation exchange and electrostatic attraction.

Low-cost and efficient activated carbon (AC) was prepared from Typha orientalis via phosphoric acid activation for chloramphenicol (CAP) removal. The adsorption capacity and mechanisms of CAP on AC were investigated. The physicochemical properties of AC were characterized by an N2 adsorption/desorption isotherm, elemental analysis, Boehm’s titration and X-ray photoelectron spectroscopy (XPS). The effects of experimental parameters were investigated to study the adsorption behaviors of CAP on AC, including contact time, initial concentration, ionic strength, and initial pH. AC had a micro-mesoporous structure with a relatively large surface area (794.8 m2/g). The respective contents of acidic and basic functional groups on AC were 2.078 and 0.995 mmol/g. The adsorption kinetic that was well described by a pseudo-second-order rate model implied a chemical controlling step. The adsorption isotherm was well fitted with the Freundlich isotherm model, and the maximum CAP adsorption capacity was 0.424 mmol/g. The ionic strength and pH had minimal effects on CAP adsorption. The dominant CAP adsorption mechanisms on AC were evaluated and attributed to π-π electron-donor-acceptor (EDA) interaction, hydrophobic interaction, in conjunction with hydrogen-bonding interaction. Additionally, AC exhibited an efficient adsorption performance of CAP in a realistic water environment.

Tartaric acid (TA) was employed to modify Zizania caduciflora (ZC)-based activated carbon during phosphoric acid activation for improving its Cr(VI) removal from aqueous solutions. The original activated carbon (AC) and TA-modified activated carbon (AC-TA) were characterized by N2 adsorption/desorption, Boehm's titration and X-ray photoelectron spectroscopy (XPS) analysis. The Cr(VI) removal abilities of AC and AC-TA were evaluated by batch sorption experiments. The residual Cr(VI) and total Cr concentration were determined to investigated the "Sorption-coupled reduction" mechanism. Equilibrium data for the Cr(VI) removal on AC and AC-TA were well described by the Freundlich model. The AC-TA exhibited much higher Cr(VI) and total Cr sorption capacities than AC. After blocking of carboxyl and hydroxyl functional groups, the carbons showed obviously higher Cr(VI) and total Cr removal than the original AC and AC-TA, indicating that electrostatic attraction played an important role on Cr(VI) removal. The higher Cr(VI) removal on AC-TA was attributed to its higher amount of oxygen-containing functional groups, which provided more electrons for Cr(VI) reduction and more positive sites for the produced Cr(III) sorption. © 2014 Elsevier B.V.

In this work, zinc borate (ZB) was employed as flame retardant for preparation of biochar (BC). A series of BC samples were generated by varying the ZB to lotus stalks (LS) ratio (0.25, 0.5 and 1.0) under different temperatures (300, 350 and 400 °C) for 1 h. The BCs were analyzed for their surface morphologies, surface areas, surface elemental compositions and yields. The results indicated that, after charring, ZB kept the structures of the produced BCs as its starting material (LS), dramatically enhancing their yields, and promoting their surface oxygen content. The BCs were used as adsorbent for removal of Ni(II) from aqueous solutions. Sorption of Ni(II) on the BCs was enhanced about 3-10 times compared with that of BCs derived from pyrolysis of LS without adding ZB. © 2014 Elsevier B.V.