ECO-FRIENDLY hybrid hydrogels for detection of phenolic RESIDUES in water using SERS.

Herein is presented a simple and sensible method to determine organic pollutants in water, based on the utilization of silver nanoparticles (AgNPs) loaded in Polyacrylamide (PAAm)/starch hybrid hydrogels combined with surface-enhanced Raman scattering (SERS) spectroscopy. The materials were characterized by swelling degree studies, UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD) and scanning electron microscopy (SEM). PAAm/starch hydrogels showed variable swelling capacity, according to the synthetic molar composition. The most promising results were attributed to lower concentrations of starch and crosslink agent (N,N'-methylenebisacrylamide - MBA). Spectroscopic analysis confirmed the formation of AgNPs, by noticing the peak at around 420 nm, due to its surface plasmon resonance (SPR) effect. The results showed that AgNPs were stabilized by hydrogels networks. The average size of the AgNPs was smaller than 100 nm and the size and quantity of nanoparticles were influenced by the molar composition of the hydrogel matrix. The SERS substrate based on the AgNPs-PAAm/starch exhibited reproducibility, stability, and limit of detection (LOD) of phenol in water of 1 × 10-8 M. The average mass of AgNPs-PAAm/starch hydrogels used for each detection analysis was around 10 mg. The spectra with enhanced intensities were possible due to a large number of hot spots generated on the AgNPs-PAAm/starch hydrogel substrate, which leads to potential use for organic pollutant detection. In addition, there is also the possibility of reusing the hydrogel matrix substrate in other analyzes.

Polymer-Decorated Cellulose Nanocrystals as Environmentally Friendly Additives for Olefin-Based Drilling Fluids.

In this study, we intended to evaluate the performance of olefin-based drilling fluids after addition of cellulose nanocrystal (CNC) derivatives. For this purpose, firstly, cellulose nanocrystals, produced from sulfuric acid hydrolysis of cotton fibers, were functionalized with poly(N-isopropylacrylamide) (PNIPAM) chains via free radicals. The samples were then characterized via Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), confocal microscopy, dynamic light scattering (DLS), and zeta potential measurements in water. The FTIR and NMR spectra exhibited the characteristic signals of CNC and PNIPAM groups, indicating successful grafting. As expected, X-ray diffractograms showed that the crystallinity of CNCs reduces after chemical modification. TGA revealed that the surface-functionalized CNCs present higher thermal stability than pure CNCs. The confocal microscopy, zeta potential, and DLS results were consistent with the behavior of cellulose nanocrystals decorated by a shell of PNIPAM chains. The fluids with a small amount of modified CNCs presented a much lower volume of filtrate after high-temperature and high-pressure (HTHP) filtration tests than the corresponding standard fluid, indicating the applicability of the environmentally friendly particles for olefin-based drilling fluids.

Polyphosphates can stabilize but also aggregate colloids.

Phosphates are well known as dispersants for a variety of colloidal particles. Here however we use rheological measurements to show that high molecular weight polyphosphates (PP) can instead act as a flocculant for LAPONITE® clay platelets. The proposed mechanism is bridging of PP between clay particle edges, leading to highly charged clusters forming a Wigner glass. Dynamic light scattering shows a bimodal cluster size distribution, independent of PP molecular weight, but the highest molecular weight gave the highest viscous and loss moduli for the PP-clay solid. These unique all-inorganic solids may have application in solid-state ionic conducting materials, controlled release fertilizers and biomedical applications.

Water-soluble carboxymethylchitosan used as corrosion inhibitor for carbon steel in saline medium.

Biodegradability and ecotoxicity of products used in oil industry are of great relevance and corrosion inhibitor could not be an exception. In earlier reports, chitosan and some derivatives were evaluated as corrosion inhibitors at acid pH, mainly due to polymer solubility. An eco-friendly corrosion inhibitor with water solubility in all pH range should be ideal, as well as that could act under the high salinity of oil field environment. Thus, herein is presented the performance of a water-soluble carboxymethylchitosan (CMC) as corrosion inhibitor in presence of chlorides (3.5% NaCl) in 1020 carbon steel, without any addition of acid or base. CMC showed good properties as corrosion inhibitor in media containing Cl-, and behaved as an anodic inhibitor. CMC exhibited inhibitory efficiency of about 80% and 67%, according to Tafel curve and electrochemical impedance, respectively, which was attributed to chemisorption mechanism (ΔGads ≈ -45 kJ/mol).

Application of guar gum in brine clarification and oily water treatment.

The increasing amount of oil wastewater is causing serious damage to the environment. Oily water is a worrisome by-product of the oil industry due to its growing volume in mature basins and complex chemical composition. Low-cost polymers are being used as alternative materials to treat oily waters after treatment by conventional methods, oil and grease (O&G) concentration being the primary parameter for final disposal. In this respect, guar gum can be used to treat petroleum-contaminated waters, with the advantage of being a low-cost, highly-hydrophilic natural polymer. In this study, guar gum, under specific conditions, shapes itself into three-dimensional structures with interesting physicochemical properties. The salting out effect occurs with reticulation of the polymeric chains by borate ions and in the presence of electrolytes, reducing the solubility of the polymeric network in the solution and leading to an electrolyte- and polymer-rich phase. When the guar gum gel was prepared in situ in the produced water, after the salting out effect, the oil was imprisoned in the interstices of the collapsed gel. The gelling guar gum was highly efficient in synthetic oily waters. In the case of initial O&G above 100ppm, the oil removal percentage was above 90%.

L-Arabinose (pyranose and furanose rings)-branched poly (vinylalcohol): enzymatic synthesis of the sugar esters followed by free radical polymerization.

Herein this study reports the successful synthesis of a new poly(vinyl alcohol) (PVA), containing L-arabinose (L-arabinopyranose and arabinofuranose isomers) branched in only two steps: (1) production of polymerizable monomers of L-arabinose isomers (pyranose and furanose forms) through enzymatic synthesis using alkaline protease from Bacillus subtilis as catalyst and two substrates: L-arabinose and Divinyl Adipate (DVA) in N,N-dimethylformamide (DMF); (2) radical polymerization of the monomers, using an initiator system consisting of potassium persulfate and hydrogen peroxide in water. The transesterification of DVA with L-arabinose was monitored via qualitative analysis by TLC, confirming the formation of the vinyl sugar ester. The acylation occurred on the two different cyclic conformations of the L-arabinose which coexist in equilibrium: (α/ß) arabinofuranose and (α/ß) arabinopyranose. The acylation positions and the chemical structure of the 5-O-vinyl adipoyl L-arabinofuranose and 4-O-vinyl adipolyl L-arabinopyranose formed were determined by 13C NMR. The surface activity of the L-arabinose esters mixture (monomers) was compared with a commercial product based on phenol formaldehyde polyoxyalkylene polyamine, largely used as surfactant in many industries. FTIR spectroscopy of the sugar ester monomers and the respective polymer were compared revealing the disappearance of the vinyl group in the polymer spectrum. The polymer number-average molar mass (Mn) and the weight-average molar mass (Mw) were determined by gel permeation chromatography (GPC) presenting the following results: 2.9 × 10(4) Da and 7.2 × 10(4) Da, respectively, and polydispersity (Mw/Mn) equal to 2.48.