Grape stalk application for caffeine removal through adsorption.

Concern over emerging pollutants presence in water resources is growing, justifying the search for alternative or additional techniques to those applied in conventional water treatment processes. Use of adsorption with agricultural wastes directly as adsorbents or as precursors for activated carbon synthesis is a viable method, combining removal efficiency, low cost and biodegradability of the material applied. This study investigated the employability of grape stalk, a waste from grape industrialization process without effective use, in caffeine removal from aqueous solution. Grape stalk was used in three different forms: raw with only grain size adjustment (GS), modified by phosphoric acid action (MGS) and as activated carbon (GSAC). In the first two cases parameters pH, residence time and adsorbent concentration were varied in order to find optimum batch process conditions. For GSAC, on the other hand, caffeine removal percentages were high even for the least amount of adsorbent that could be measured with acceptable accuracy, which did not justify concentration parameter variation. Better adsorption capacities were observed in acidic solutions, with optimum pH values being considered as 2.0 for GS and MGS and 4.0 for GSAC. Optimum residence time and adsorbent concentration were 40 min and 25 g L-1 (GS), 30 min and 15 g L-1 (MGS) and 30 min (GSAC). Moreover, equilibrium was evaluated through adsorption isotherms construction, which were best represented by Sips model, displaying determination coefficients R2 equal to 0.994, 0.999 and 0.987 and maximum adsorption capacities equal to 89.2, 129.6 and 916.7 mg g-1. Adsorbents particular characteristics such as specific surface areas and micropore volumes were also determined, resulting in 6.23, 4.21 and 1099.86 m2 g-1 and 0.003, 0.002 and 0.568 cm3 g-1 for GS, MGS and GSAC, respectively.

Grape stalk valorization for fermentation purposes.

White and red grape stalks biomass were fractioned to maximize its economic value by the production of fermentable sugars, as other value streams. High yields of extractives and lignin were first obtained, originating a biomass rich in cellulose and hemicellulose, which was subject to acid and enzymatic hydrolysis for production of fermentable sugars. Higher concentrations of sugars were obtained by enzymatic than by dilute acid hydrolysis. These biosugars were used for fermentation processes with Pichia stipitis and Saccharomyces cerevisiae. The presence of higher quantities of xylose favoured P. stipitis to produce higher ethanol yields than S. cerevisiae which is glucose lover. Cellulose nanocrystals were produced from the resulting biomass without monosaccharides. For the first time an integrated valorization of grape stalks followed by an application of one of the valorized streams is presented.

Combined effects of Diospyros lotus leaf and grape stalk extract in high-fat-diet-induced obesity in mice.

The aim of this study was to investigate the combined effects of Diospyros lotus leaves extracts (DLE) and Muscat Bailey A grape stalk extracts (MGSE) in obesity induced by high-fat diet (HFD) in mice. The mice were fed with HFD and orally administered daily with DLE, MGSE, a mixture of DLE and MGSE, and Garcinia cambogia extract over a period of 16 weeks. The results revealed that daily administration of DLE and MGSE mixtures markedly prevented HFD-induced weight gain, plasma lipid profile, hepatic steatosis, hepatic fibrosis, diabetic symptoms, and the risk of developing cardiovascular diseases. Also, DLE and MGSE mixtures administration greatly prevented oxidative stress and liver toxicity. The combined effects of DLE and MGSE mixtures were higher than effects of the single extracts and of G. cambogia, a plant known for its anti-obesity effects. In summary, these findings demonstrated that DLE and MGSE mixtures, exhibit anti-obesity activity in HFD-fed mice.

Green Synthesis of Ag Nanoparticles Using Grape Stalk Waste Extract for the Modification of Screen-Printed Electrodes.

The chemical synthesis of silver nanoparticles (Ag-NPs) by using an environmentally friendly methodology for their preparation is presented. Thus, considering that plants possess components that can act as reducing agents and stabilizers in nanoparticles' production, the synthesis of Ag-NPs by using an extract aqueous solution of grape stalk waste as a reducing and capping agent is studied. First, the total polyphenols and reducing sugars contained in the produced extracts at different conditions are characterized. After that, Ag-NPs are synthesized regarding the interaction of Ag ions (from silver nitrate) and the grape stalk extract. The effect of temperature, contact time, extract/metal solution volume ratio and pH solution in the synthesis of metal nanoparticles are also studied. Different sets of nanoparticle samples are characterized by means of Electron Microscopy coupled with Energy Dispersive X-Ray for qualitative chemical identification. Ag-NPs with an average diameter of 27.7 ± 0.6 nm are selected to proof their suitability for sensing purposes. Finally, screen-printed electrodes modified with Ag-NPs are tested for the simultaneous stripping voltammetric determination of Pb(II) and Cd(II). Results indicate good reproducibility, sensitivity and limits of detection around 2.7 µg L-1 for both metal ions.

Simultaneous and automated monitoring of the multimetal biosorption processes by potentiometric sensor array and artificial neural network.

In this communication, a new methodology for the simultaneous and automated monitoring of biosorption processes of multimetal mixtures of polluting heavy metals on vegetable wastes based on flow-injection potentiometry (FIP) and electronic tongue detection (ET) is presented. A fixed-bed column filled with grape stalks from wine industry wastes is used as the biosorption setup to remove the metal mixtures from the influent solution. The monitoring system consists in a computer controlled-FIP prototype with the ET based on an array of 9 flow-through ion-selective electrodes and electrodes with generic response to divalent ions placed in series, plus an artificial neural network response model. The cross-response to Cu(2+), Cd(2+), Zn(2+), Pb(2+) and Ca(2+) (as target ions) is used, and only when dynamic treatment of the kinetic components of the transient signal is incorporated, a correct operation of the system is achieved. For this purpose, the FIA peaks are transformed via use of Fourier treatment, and selected coefficients are used to feed an artificial neural network response model. Real-time monitoring of different binary (Cu(2+)/ Pb(2+)), (Cu(2+)/ Zn(2+)) and ternary mixtures (Cu(2+)/ Pb(2+)/ Zn(2+)), (Cu(2+)/ Zn(2+)/ Cd(2+)), simultaneous to the release of Ca(2+) in the effluent solution, are achieved satisfactorily using the reported system, obtaining the corresponding breakthrough curves, and showing the ion-exchange mechanism among the different metals. Analytical performance is verified against conventional spectroscopic techniques, with good concordance of the obtained breakthrough curves and modeled adsorption parameters.