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Despite the immense number of research on the activated carbon (AC) preparation for wastewater treatment, fewer fractions have been devoted to the microwave-assisted activation route, which is unfortunate considering its advantageous features. In regards, this study explores the feasibility of a simple and rapid microwave-assisted activation method to generate AC from the spent coffee ground (SCG) under various microwave powers (100-450 W). The physicochemical properties of the generated ACs were studied by Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption-desorption, and X-ray diffraction analysis. As attained, lower microwave powers generated ACs with higher surface areas, pore volumes, and pore size as well as dominant OH and C=O spectral bands, which can correspond to higher adsorption sites for a more effective methylene blue (MB) removal process. In parallel, the adsorption tests demonstrated that the lowest microwave power sample (SCG-100) exhibited the highest MB adsorption at equilibrium (35 ± 1.75 mg g−1) in the optimum conditions of 25 mg L−1 MB solution, pH 8, 6 hour duration, and 0.025 g adsorbent. The kinetic and isotherm studies revealed the MB adsorption onto SCG-100 was defined by the pseudo-first-order (R2=0.9462) and Langmuir isotherm (R2= 0.9617) models respectively. Thermodynamically, the adsorption process occurred in an exothermic, and spontaneous manner. The water quality analysis data further found that the total organic compound, biological, and chemical oxygen demand were successfully decreased in a 6-hour period. Therefore, it can be concluded that the microwave activation method was capable of generating highly functional absorbent material for pollutant adsorption application. [ABSTRACT FROM AUTHOR] more...

A method was developed for the simultaneous extraction of herbicides such as 2,4 D, MCPA, ametryn, chlorothalonil, and bromacil in water and vegetable samples by emulsification liquid-liquid microextraction with fatty acids based hydrophobic deep eutectic solvents (DES). The DES were synthesised by mixing several fatty acids ratios that functioned as both the hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD). Using the DES as the microextraction solvent, several vital parameters were optimised, including the type and volume of hydrophobic DES, pH of the sample, sonication time, and type and volume of emulsifier. Then, the extracted herbicides were back-extracted into phosphoric acid solution (0.05 M). The detection limits were in the range of 0.01–2.5 ng mL−1, the quantification limits were in the range of 0.03–8.3 ng mL−1, and recoveries were in the range of 73.1–98.8% with RSD <10%. The greenness assessment using Analytical Eco-Scale and AGREE (Analytical GREEnness Metric Approach System) exhibited that the emulsification liquid-liquid microextraction method using DES can be considered as simple, practical, and environmentally friendly. [ABSTRACT FROM AUTHOR] more...

The presence of pharmaceuticals in aquatic systems is a matter of great concern. As a result of their high solubility and low volatility, their removal has been very challenging. In this work, the synthesis, characterisation and adsorption study of graphene oxide-based magnetic nanoparticles (GO@Fe3O4) were explored for the removal of fluoroquinolones (FQs). GO@Fe3O4 adsorbent was synthesised by a one-step co-precipitation method using ammonium ferrous sulphate ((NH4)2FeSO4) and ferric chloride hexahydrate (FeCl3 · 6H2O) as iron sources and ammonium solution as precipitant. The removal of four FQs (ofloxacin, enrofloxacin, sparfloxacin. and gemifloxacin) by GO@Fe3O4 adsorbent was explored. The effect of contact time, initial pH of the solution, initial FQs concentration on the removal efficiency, and reusability were investigated. The pseudo-second-order kinetic model represented the adsorption process for GO@Fe3O4 adsorbent. The Freundlich isotherm model was a better fit with adsorption capacities of 44.4, 40.8, 64.0, and 51.8 mg/g for ofloxacin, enrofloxacin, sparfloxacin, and gemifloxacin, respectively. Under optimised conditions, GO@Fe3O4 adsorbent was successfully applied for the removal of FQs in water samples from the Langat River basin. The results showed enhanced sorption capacity and high removal efficiency towards for FQs removal from an aqueous solution and has the potential to be an alternative adsorbent. [ABSTRACT FROM AUTHOR] more...

New S-quinolin-2-yl-methyl-dithiocarbazate-based magnetic adsorbent (MNP-SQ2MDTC) for magnetic solid phase extraction (MSPE) was developed for the determination of Cd2+ and Cu2+ in water samples. The surface of MNP was first coated with (3-aminopropyl) triethoxysilane (APTES) as cross-linker and then SQ2MDTC incorporated covalently to the coated MNP. The newly prepared MNP-SQ2MDTC was analysed by Fourier Transform infrared (FT-IR), X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDX), vibrating-sample magnetometry (VSM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET). Under optimal MSPE conditions (20 mg adsorbent dispersed in 25 mL of sample which adjusted to pH 6.0 and sonicated for 10 min, before desorbed in 0.5 mL of 1 M HClO4 and sonicated for 5 min), the validation method revealed a good linearity (0.1–5.0 µg mL−1) with the coefficient of determination (R2) in the range of 0.995–0.996 for the samples. The limits of detection (LOD) of the developed method for Cd2+ and Cu2+ were found to be 0.054 and 0.040 µg mL−1, and limit of quantification (LOQ) were 0.180 and 0.134 µg mL−1, respectively. The recoveries of Cd2+ ranged from 75.6% to 93.9% and from 81.5% to 98.7% for Cu2+. To the best of our knowledge, this is the first study that have investigated the use of magnetic nanoparticles coated SQ2MDTC for determination of Cd2+ and Cu2+ in water samples analysis based on complexation of the metal ions to the surface of amino groups. [ABSTRACT FROM AUTHOR] more...

3-Monochloropropane-1,2-diol (3-MCPD) monoesters are a form of 3-MCPD esters known as potential food contaminant that may occur in a variety of food samples. A dispersive solid-phase extraction (dSPE) was developed to provide clean-up and pre-concentration in the determination of 1-palmitoyl-3-MCPD and 1-oleoyl-3-MCPD prior to gas chromatography-flame ionization detector analysis (GC-FID). Dispersive solid-phase extraction (dSPE) involves the direct addition of C18 sorbent into the sample solution and the subsequent collection of the aqueous solution. After separation of target analytes with matrices, the analytes were quantified using GC-FID. Under optimum conditions (6 mL of 80:20 v/v of ACN; ethyl acetate as extraction solvent, 10 mg of C18 sorbent, 10 µL of reconstituted solvent volume, and 300 µL of sample volume), the proposed method was validated and the calibration curve was found to be linear with R2 > 0.998. The limit of detection (LOD) of 1.03 mg L−1 and 2.00 mg L−1 were obtained for 1-palmitoyl-3-MCPD and 1-oleoyl-3-MCPD, respectively, whereby the limit of quantification (LOQ) obtained for 1-palmitoyl-3-MCPD and 1-oleoyl-3-MCPD were 3.43 mg L−1 and 6.68 mg L−1, respectively. The developed method was applied to seven palm oil-based food samples where the amount of 3-MCPD detected was higher than recommended by the European Food Safety and Authority (ESFA). The recoveries for spiked samples ranged from 59.3 to 115.9% and the relative standard deviation (RSD) for inter-day and intra-day was less than 15%. The method was applied for the determination of 3-MCPD monoesters in palm oil-based food samples. [ABSTRACT FROM AUTHOR] more...