PMMA/SWCNT Composites with Very Low Electrical Percolation Threshold by Direct Incorporation and Masterbatch Dilution and Characterization of Electrical and Thermoelectrical Properties.

In the present study, Poly(methyl methacrylate) (PMMA)/single-walled carbon nanotubes (SWCNT) composites were prepared by melt mixing to achieve suitable SWCNT dispersion and distribution and low electrical resistivity, whereby the SWCNT direct incorporation method was compared with masterbatch dilution. An electrical percolation threshold of 0.05-0.075 wt% was found, the lowest threshold value for melt-mixed PMMA/SWCNT composites reported so far. The influence of rotation speed and method of SWCNT incorporation into the PMMA matrix on the electrical properties and the SWCNT macro dispersion was investigated. It was found that increasing rotation speed improved macro dispersion and electrical conductivity. The results showed that electrically conductive composites with a low percolation threshold could be prepared by direct incorporation using high rotation speed. The masterbatch approach leads to higher resistivity values compared to the direct incorporation of SWCNTs. In addition, the thermal behavior and thermoelectric properties of PMMA/SWCNT composites were studied. The Seebeck coefficients vary from 35.8 µV/K to 53.4 µV/K for composites up to 5 wt% SWCNT.

Desalination and Detoxification of Textile Wastewater by Novel Photocatalytic Electrolysis Membrane Reactor for Ecosafe Hydroponic Farming.

In this study, a novel photoelectrocatalytic membrane (PECM) reactor was tested as an option for the desalination, disinfection, and detoxification of biologically treated textile wastewater (BTTWW), with the aim to reuse it in hydroponic farming. The anionic ion exchange (IEX) process was used before PECM treatment to remove toxic residual dyes. The toxicity evaluation for every effluent was carried out using the Vibrio fischeri, Microtox® test protocol. The disinfection effect of the PECM reactor was studied against E. coli. After PECM treatment, the 78.7% toxicity level of the BTTWW was reduced to 14.6%. However, photocatalytic desalination during treatment was found to be slow (2.5 mg L-1 min-1 at 1 V potential). The reactor demonstrated approximately 52% COD and 63% TOC removal efficiency. The effects of wastewater reuse on hydroponic production were comparatively investigated by following the growth of the lettuce plant. A detrimental effect was observed on the lettuce plant by the reuse of BTTWW, while no negative impact was reported using the PECM treated textile wastewater. In addition, all macro/micronutrient elements in the PECM treated textile wastewater were recovered by hydroponic farming, and the PECM treatment may be an eco-safe wastewater reuse method for crop irrigation.

Development of an automated flow injection analysis system for determination of phosphate in nutrient solutions.

BACKGROUND: A fully automated flow injection analysis (FIA) system was developed for determination of phosphate ion in nutrient solutions. This newly developed FIA system is a portable, rapid and sensitive measuring instrument that allows on-line analysis and monitoring of phosphate ion concentration in nutrient solutions. The molybdenum blue method, which is widely used in FIA phosphate analysis, was adapted to the developed FIA system. The method is based on the formation of ammonium Mo(VI) ion by reaction of ammonium molybdate with the phosphate ion present in the medium. The Mo(VI) ion then reacts with ascorbic acid and is reduced to the spectrometrically measurable Mo(V) ion. New software specific for flow analysis was developed in the LabVIEW development environment to control all the components of the FIA system. The important factors affecting the analytical signal were identified as reagent flow rate, injection volume and post-injection flow path length, and they were optimized using Box-Behnken experimental design and response surface methodology. RESULTS: The optimum point for the maximum analytical signal was calculated as 0.50 mL min-1 reagent flow rate, 100 µL sample injection volume and 60 cm post-injection flow path length. The proposed FIA system had a sampling frequency of 100 samples per hour over a linear working range of 3-100 mg L-1 (R2 = 0.9995). The relative standard deviation (RSD) was 1.09% and the limit of detection (LOD) was 0.34 mg L-1 . CONCLUSION: Various nutrient solutions from a tomato-growing hydroponic greenhouse were analyzed with the developed FIA system and the results were found to be in good agreement with vanadomolybdate chemical method findings. © 2018 Society of Chemical Industry.

Preparation of electrochemically treated nanoporous pencil-graphite electrodes for the simultaneous determination of Pb and Cd in water samples.

A simple and rapid analytical method of determining Pb2+ and Cd2+ in water samples using an electrochemically pretreated pencil-graphite electrode (EP-PGE) is proposed for the first time in the literature. An electrochemically pretreated pencil-graphite electrode was prepared by performing potential cycling between -0.3 V and 2.0 V in 0.1 mol L-1 H3PO4 solution to improve its ability to electrochemically sense Pb2+ and Cd2+ ions. Square-wave anodic stripping voltammetry (SWASV) was used as the electroanalytical method. The electroanalytical parameters that influence the stripping determination of Pb2+ and Cd2+ were optimized based on experimental results. The magnitude of the peak oxidation current was adjusted in order to optimize the value of each parameter. Applying the resulting disposable electrode under the optimized conditions led to good selectivity and sensitivity in the determination of Pb2+ and Cd2+ ions. Interference from coexisting ions was also investigated. The resulting sensor was successfully tested by applying it to a standard reference water sample. Under the optimized conditions, the limits of detection were 0.46 µg L-1 for Pb2+ and 1.11 µg L-1 for Cd2+ using the electrode. Relative standard deviations (%RSD) were 2.76 for Pb2+ and 2.85 for Cd2+. The linear working ranges of the electrode for Pb2+ and Cd2+ ion detection were 5-45 µg L-1 and 10-40 µg L-1, respectively. Graphical abstract Preparation of nanoporous pencil-graphite electrode by cyclic voltammetry and stripping voltammetric screening of Pb and Cd.