Comprehensive Characterization of Commercial Reverse Osmosis Membranes through High-Temperature Cross-Flow Filtration.

Developing thermally stable reverse osmosis membranes is a potential game-changer in high-temperature water treatment. In this work, the performance of three commercial reverse osmosis membranes was evaluated with a series of high-temperature filtrations. The membranes were tested with different filtration methodologies: long-term operation, cyclic tests, controlled stepwise temperature increment, and permeability tests. The morphological and physiochemical characterizations were performed to study the impact of high-temperature filtration on the membranes' chemical composition and morphological characteristics. An increase in the temperature deteriorated the membrane performance in terms of water flux and salt rejection. Flux decline at high temperatures was recognized as the primary concern for high-temperature filtrations, restricting the applications of commercial membranes for long-term operations. This research provides valuable insights for researchers aiming to thoroughly characterize reverse osmosis membranes at high temperatures.

Exploring Alternatives to Polyacrylamide: A Comparative Study of Novel Polymers in the Flocculation and Dewatering of Iron Ore Tailings.

Despite being widely used in tailings treatment, polyacrylamide continues to face performance challenges. In this study, two commercial polyacrylamides with different molecular weights were used to flocculate iron ore tailings and their performance was compared with two polymers designed to treat oil sand tailings: poly(vinylbenzyl)trimethylammonium chloride and partially hydrolyzed poly(methyl acrylate) grafted onto ethylene-propylene-diene copolymer backbones. The polyacrylamide with the highest molecular weight performed better than the one with the lowest molecular weight, but its efficiency was still considerably lower than what would be desired for good solid-liquid separation. The new polymer flocculants performed better than the commercially available polyacrylamides but retained high amounts of water in the sediments. This comparison shows that polymers other than polyacrylamide may be used to treat iron ore tailings.

Naphthalene diimide-based n-type small molecule organic mixed conductors for accumulation mode organic electrochemical transistors.

Organic mixed ionic-electronic conductors (OMIECs), which transport both ionic and electronic charges, development are important for progressing bioelectronic and energy storage devices. The p-type OMIECs are extensively investigated and used in various applications, whereas the n-type ones lag far behind due to their moisture and air instability. Here, we report the synthesis of the novel n-type naphthalene diimide (NDI)-based small-molecule OMIECs for organic electrochemical transistors (OECTs). The electro-active NDI molecule with the linear ethylene glycol side chains is a promising candidate for n-type channel material to obtain accumulation mode OECTs. This NDI-based small-molecule OMIEC, gNDI-Br2, demonstrates ion permeability due to the attachment of the glycol side chains with optimized ionic-electronic conductions. OECT devices with gNDI-Br2 channel material displays excellent performance in water and ambient stability. OECTs fabricated with two different concentrations, 50 mg mL-1 and 100 mg mL-1 of gNDI-Br2 demonstrate a transconductance value of 344 ± 19.7 µS and 814 ± 124.2 µS with the mobility capacitance product (µC*) of 0.13 ± 0.03 F cm-1 V-1 s-1 and 0.23 ± 0.04 F cm-1 V-1 s-1, respectively. These results demonstrate the n-type OMIEC behaviour of the NDI-based small-molecule and its applicability as an OECT channel material.

Facile and Efficient Phase-Selective Powder Polymer Organogelator for Oil Spill Remediation.

Phase-selective organogelators that gel oils from oil/water mixtures are useful to remediate oil spills on water. We designed and synthesized polymer organogelators, poly(styrene-co-10-undecenoic acid) with five different 10-undecenoic acid contents that could be added as powders at room temperature to gel oils with different viscosities. The morphologies and mechanical strengths of the gels were investigated using field-emission electron microscopy and rheological measurements, respectively. The gels formed porous fibrillar structures and had high stiffness. Fourier transformm infrared (FTIR) spectroscopy studies of these gels showed that hydrogen bonding and van der Waals forces helped create three-dimensional networks. The straightforward synthesis procedure, room-temperature conditions, and easy powder delivery make poly(styrene-co-10-undecenoic acid) an attractive alternative to existing oil spill response methods.

Polystyrene magnetic nanocomposite blend: An effective, facile, and economical alternative in oil spill removal applications.

Finding an efficient and economical method to remediate oil spills on water is a priority worldwide. In this article, we propose a solution to this problem using polystyrene magnetic nanocomposite blends composed of polystyrene chains grafted on the surface of silica coated on iron oxide nanoparticles and polystyrene. The hydrophobic and oleophilic magnetic polymer nanocomposite collected oil from the water surface quickly and efficiently. However, when the magnetic polymer nanocomposite was blended with polystyrene, the resulting material also absorbed oil efficiently from the water surface. The blending technique made it easier to prepare the absorbent and dramatically decreased its cost. These new absorbents absorbed oil up to 5 times their own weight in only 5 minutes. The excellent hydrophobicity, low density, and easy magnetic separation makes these new absorbents a promising alternative to recover oil from spilled in fresh and marine water.

Validation of the IBD-Disk in a Portuguese cohort.

OBJECTIVE: The aim of this study was to validate the IBD-Disk in a Portuguese cohort according to the COnsensus-based Standards for the selection of the health Measurement INstruments (COSMIN) recommendations. METHODS: After translation of the original IBD-Disk to Portuguese, a group of IBD patients was invited to complete the IBD-Disk at baseline (T0), after 1-4 weeks (T1) and after more than 3 months (T2), from July 2020 to February 2021. At T0 and T2, the patients also completed the IBD Disability Index. We evaluated reliability (internal consistency, test-retest, interrater reliability and measurement error), construct validity, responsiveness, interpretability of IBD-Disk, sociodemographic and clinical factors associated with IBD-Disk. RESULTS: At T0, 154 patients (107 - Crohn's disease; 46 - ulcerative colitis) completed the IBD-Disk; 1 - IBD-unclassified). At T1 and T2, 64 and 114 patients repeated the questionnaire, respectively. Factor analysis confirmed the unidimensionality of the scale and reduced the final version to 10 items. Internal consistency was excellent with a Cronbach's α of 0.916. The intraclass correlation coefficient was 0.95 for test-retest (T0 and T1). To evaluate construct validity, the IBD-Disk was compared with the IBD Disability Index and Manitoba IBD Index with a significative positive correlation (r = 0.850 and r = 0.459, respectively; P < 0.001 for both). IBD-Disk scores ranged from 0 to 93 with a mean of 38.18 ± 25.39. Female sex, professional inactivity, longer IBD duration and clinical activity were associated with significantly higher IBD-Disk scores. CONCLUSION: The Portuguese version of IBD-Disk is a reliable and valid tool to assess disability in Portuguese IBD patients.

Nanodiamond-Enabled Thin-Film Nanocomposite Polyamide Membranes for High-Temperature Water Treatment.

Despite growing demands for high-temperature wastewater treatment, most available polymeric membranes are limited to mild operating temperatures (<50 °C) and become less efficient at high temperatures. Herein we show how to make thermally stable reverse osmosis thin-film nanocomposite (TFN) membranes by embedding nanodiamond (ND) particles. Polyamide composite layers containing different loadings of surface-modified ND particles were synthesized through interfacial polymerization. The reactive functional groups and the hydrophilic surface of the NDs intensified the interactions of the nanoparticles with the polymer matrix and increased the surface wettability of the TFN membranes. Contact angle measurement showed a maximum decrease from 88.4° for the pristine membrane to 58.3° for the TFN membrane fabricated with 400 ppm ND particles. The addition of ND particles and ethyl acetate created larger surface features on the polyamide surface of TFN membranes. The average roughness of the membranes increased from 108.4 nm for the pristine membrane to 177.5 nm for the TFN membrane prepared with highest ND concentration. The ND-modified TFN membranes showed a higher pure water flux (up to 76.5 LMH) than the pristine membrane (17 LMH) at ambient temperature at 220 psi and room temperature. The TFN membrane with the highest loading of ND particles overcame the trade-off relation between the water flux and NaCl rejection with 76.5 LMH and 97.3% when 2000 ppm of NaCl solution was filtered at 220 psi. Furthermore, with increasing ND concentration, the TFN membrane showed a lower flux decline at high temperatures over time. The TFN400 prepared with 400 ppm of m-phenylene diamine functionalized ND particles had a 13% flux decline over a 9 h filtration test at 75 °C. This research provides a promising path to the development of high-performance TFN membranes with enhanced thermal stability for the treatment of wastewaters at high temperatures.

Fabrication of Highly Permeable and Thermally Stable Reverse Osmosis Thin Film Composite Polyamide Membranes.

Developing thermally stable polymer membranes for high-temperature water treatment is in high demand, as the recommended usage temperatures of most commercial membranes are lower than 50 °C. In this study, we synthesized novel thin film composite polyamide membranes by modifying the chemical structure of their selective layers. Triaminopyrimidine was used to synthesize a polyamide selective layer with high cross-linking density over a microporous poly(ether sulfone) support. The addition of triamiopyrimidine to the classic m-phenylenediamine/trimesoyl chloride combination remarkably improved the permeation of the membranes. All synthesized thin film composite membranes showed consistent permeate flux for 9 h of operation at 75 °C with only a slight reduction in salt rejection. This study provides a promising and reproducible methodology to develop thermally stable high-flux thin film composite membranes, opening up a new paradigm for high-temperature water treatment processes.

Cross-Sectional Study to Assess Endoscopic Ultrasound Practice in Portugal.

BACKGROUND: Despite the increasing number of national departments performing endoscopic ultrasound (EUS), there are no official data regarding clinical EUS practice in Portugal. OBJECTIVES: We aimed to evaluate the current practice of EUS in Portugal. METHODS: By email, we invited 1 physician of each one of the 26 national Gastroenterology Departments which perform EUS to complete a survey questionnaire available on the Google Forms platform. The online questionnaire was available from September 2017 until February 2018 and was answered only by physicians who perform EUS. RESULTS: A total of 21/26 (80.8%) national Gastroenterology Departments answered the questionnaire. In Portugal, there are 42 echoendoscopes in total; most of the echoendoscopy units have only 1 EUS processor (81%), 1 radial echoendoscope (66.7%), 1 linear echoendoscope (76.2%), 1 anorectal probe (57.1%), but no miniprobes (85.7%). About 81% have histological core acquisition needles. In 81% of the units, there are at least 2 ultrasonographers who perform echoendoscopy together (at least 2 ultrasonographers per EUS) in 47.6% of these departments. The ultrasonographers also performed abdominal ultrasound (US), anal US, and endoscopic retrograde cholangiopancreatography in 71.4, 66.7, and 42.9%, respectively. The echoendoscopy units have 2.4 ± 1.1 periods of echoendoscopy per week and 4 ± 1.5 EUS per period (499.2 ± 416.8 EUS per year). Subepithelial lesions and biliopancreatic lesion evaluation as well as gastrointestinal neoplasia staging were the most common EUS indications. The number of FNA (fine-needle aspirations) ranges from 10 to 160/year. Rapid on-site evaluation (ROSE) is available in 60% of units and is performed by the cytopathologist (66.7%) in the majority of cases. The main reason for omitting ROSE is the limited pathology staff. Cytopathological material is prepared by the ultrasonographer in 25% of the units. Air drying (50%) and formalin (50%) are most frequently used to fix and preserve smears, respectively. Pancreatic pseudocyst drainage (66.7%), celiac plexus neurolysis (52.4%) and pancreatic necrosectomy (42.9%) are the most widespread therapeutic procedures. CONCLUSIONS: This survey provides the first insight into the current status of digestive echoendoscopy in Portugal. There is a great variability in diagnostic and therapeutic echoendoscopy practice.

INTRODUÇÃO: Apesar do crescente número de serviços nacionais a realizar ecoendoscopia digestiva, não existem dados sobre a prática da ecoendoscopia no nosso país. OBJETIVOS: Pretendemos avaliar a prática da ecoendoscopia em Portugal. MÉTODOS: Por e-mail convidámos um elemento de cada dos 26 serviços nacionais de Gastrenterologia que realizam ecoendoscopia a preencher um questionário disponível na plataforma google forms. O questionário esteve disponível via online de setembro de 2017 a fevereiro de 2018 e foi respondido apenas por médicos que realizam ecoendoscopia. RESULTADOS: Obtivemos resposta de 21 dos 26 serviços convidados (80.8%). Em Portugal existe um total de 42 ecoendoscópios. A maioria das unidades possui 1 ecógrafo (81%), 1 ecoendoscópio radial (66.7%), 1 eco endoscópio linear (76.2%), 1 sonda rectal (57.1%) mas não dispõem de mini-sondas (85.7%). 81% dispõem de agulhas de aquisição de core histológico. Em 81% dos serviços existem pelo menos 2 ecoendoscopistas que realizam ecoendoscopia em conjunto em 47.6% dos serviços. Os ecoendoscopistas também realizam ecografia abdominal, ecografia anal e colangiopancreatografia retrógrada endoscópica em 71.4, 66.7 e 42.9% respectivamente. Os serviços têm em média 2.4 ± 1.1 períodos de ecoendoscopia/ semana realizando em média 4 ± 1.5 ecoendoscopia/ período (499.2 ± 416.8 ecoendoscopias/ano). A avaliação de lesões subepiteliais e bilio-pancreática, assim como o estadiamento de neoplasias do tubo digestivo são as indicações mais frequentes para a realização de ecoendoscopia. O número de punções diagnósticas guiadas por ecoendoscopia varia entre 10 e 160/ano. A maioria dos serviços (60%) dispõe de rapid on-site pathological evaluation (ROSE) que é realizada pelo citopatologista na maioria das vezes (66.7%). A carência de funcionários nas unidades de Anatomia Patológica é o principal motivo para a ausência de ROSE. A preparação do material citopatológico é realizada pelo ecoendoscopista em 25% dos serviços. A secagem ao ar (50%) e o formol (50%) são o método de fixação dos esfregaços e o meio de preservação mais usados, respetivamente. A drenagem de pseudocisto pancreático (66.7%), neurólise do plexo celíaco (52.4%) e necrosectomia pancreática (42.9%) são os procedimentos terapêuticos mais disseminados. CONCLUSÕES: Este trabalho fornece os primeiros dados sobre a prática de ecoendoscopia digestiva em Portugal. Existe uma grande variabilidade nos exames diagnósticos e terapêuticos.

Removal of Heavy Metal Water Pollutants (Co2+ and Ni2+) Using Polyacrylamide/Sodium Montmorillonite (PAM/Na-MMT) Nanocomposites.

Nanocomposites composed of polyacrylamide and nanoclay were synthesized via free-radical cross-linking polymerization and used to adsorb Co2+ and Ni2+ ions from water. The polyacrylamide (PAM)/sodium montmorillonite (Na-MMT) nanocomposites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy to confirm the interaction between montmorillonite and the polymer matrix. The effects of pH and heavy metal ion concentration on the adsorption capacity of PAM/Na-MMT were evaluated to determine suitable operating conditions for further experiments. Batch adsorption experimental data were fitted to Langmuir and Freundlich models, which provided information about the adsorption mechanism and the adsorbent surface. The highest Ni2+ removal yield was found to be 99.3% using the 2:1 (w/w) nanocomposite at pH 6 in 100 ppm of Ni2+ solution. The Co2+ removal yield was 98.7% at pH 6 in 60 ppm of Co2+ solution using the 4:1 (w/w) nanocomposite. These results were higher than those obtained by polyacrylamide and nanoclay under the same conditions (removal yield between 87.40 and 94.50%), indicating that PAM/Na-MMT nanocomposites remove heavy metal water pollutants more efficiently and can be used as a novel adsorbent for further industrial applications.

The main determinants of disability in IBD and its relationship to optimism

Background and aim: inflammatory bowel disease (IBD) is a potentially disabling chronic disease that negatively affects many aspects of the patients' life. This study aimed to assess the IBD-associated disability in the outpatient setting and analyze how optimism and disability are related. Methods: a cross-sectional study was performed via the application of the Portuguese version of the IBD-Disability Index (PT-IBD-DI) and the Revised Life Orientation Test (PT-LOT-R) for the assessment of disability and optimism, respectively. Results: a total of 143 patients were analyzed, the mean age was 38 +/- 13 years, 50% were females and 51% had UC. The mean PT-IBD-DI score was 22 +/- 17, which was classified as follows: 0-20: no disability; 20-35: mild disability; 35-50: moderate disability; and 50-100: severe disability. There were no significant differences between Crohn's disease (CD) and ulcerative colitis (UC) (p = 0.944). Female gender (p = 0.001), low level of education (p = 0.018), the number of days out of work (p = 0.020), rheumatologic manifestations (p = 0.005), the number of comorbidities (p = 0.002), the use psychotropic drugs (p = 0.043) and low PT-LOT-R scores (p < 0.001) were associated with higher IBD-DI scores according to the univariate analysis. According to the linear regression analysis, only female sex (p = 0.001), the number of comorbidities (p = 0.034) and low PT-LOT-R scores (p < 0.001) were associated with higher PT-IBD-DI scores. Optimism correlated inversely with PT-IBD-DI scores (ρ = -0.345, p < 0.001). Conclusion: IBD outpatients reported low levels of IBD-disability (mild disability: PT-IBD-DI score 20-35). Comorbidities and psychological factors (optimism) emerged as the main predictive factors of increased disability, reinforcing the importance of a multidisciplinary approach for these patients

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Development and application of an amylopectin-graft-poly(methyl acrylate) solidifier for rapid and efficient containment and recovery of heavy oil spills in aqueous environments.

Effective oil spill preparedness and response are crucial to ensure environmental protection and promote the responsible development of the petroleum industry. Hence, interest in developing new approaches and/or improving existing oil spill response measures has increased greatly in the past decade. Solidifiers are an attractive and underutilized option to mitigate the effects of oil spills, as they interact with oil to contain the spill, prevent it from spreading, and facilitate its removal from the environment. In this work, we have synthesized an inexpensive and easy-to-make natural-based sorbent, a subclass of solidifiers. Our amylopectin-graft-poly(methyl acrylate) (AP-g-PMA) sorbent is highly oleophilic and hydrophobic, and selectively solidifies diluted bitumen and conventional crude oil from biphasic mixtures of oil and water. The complete solidification of conventional crude oil and diluted bitumen by the AP-g-PMA sorbent occurs within 8 and 32 min, respectively, and even a low solidifier-to-oil ratio of 4% w/w is sufficient to enable complete recovery of diluted bitumen. This innovative natural-based polymeric sorbent may be applied as a key component of oil spill response procedures, especially for heavy oils. The AP-g-PMA sorbent combines the biodegradability and non-toxicity of the amylopectin with the hydrophobicity and oleophilicity of the synthetic polymer poly(methyl acrylate).

The main determinants of disability in IBD and its relationship to optimism.

BACKGROUND AND AIM: inflammatory bowel disease (IBD) is a potentially disabling chronic disease that negatively affects many aspects of the patients' life. This study aimed to assess the IBD-associated disability in the outpatient setting and analyze how optimism and disability are related. METHODS: a cross-sectional study was performed via the application of the Portuguese version of the IBD-Disability Index (PT-IBD-DI) and the Revised Life Orientation Test (PT-LOT-R) for the assessment of disability and optimism, respectively. RESULTS: a total of 143 patients were analyzed, the mean age was 38 ± 13 years, 50% were females and 51% had UC. The mean PT-IBD-DI score was 22 ± 17, which was classified as follows: 0-20: no disability; 20-35: mild disability; 35-50: moderate disability; and 50-100: severe disability. There were no significant differences between Crohn's disease (CD) and ulcerative colitis (UC) (p = 0.944). Female gender (p = 0.001), low level of education (p = 0.018), the number of days out of work (p = 0.020), rheumatologic manifestations (p = 0.005), the number of comorbidities (p = 0.002), the use psychotropic drugs (p = 0.043) and low PT-LOT-R scores (p < 0.001) were associated with higher IBD-DI scores according to the univariate analysis. According to the linear regression analysis, only female sex (p = 0.001), the number of comorbidities (p = 0.034) and low PT-LOT-R scores (p < 0.001) were associated with higher PT-IBD-DI scores. Optimism correlated inversely with PT-IBD-DI scores (ρ = -0.345, p < 0.001). CONCLUSION: IBD outpatients reported low levels of IBD-disability (mild disability: PT-IBD-DI score 20-35). Comorbidities and psychological factors (optimism) emerged as the main predictive factors of increased disability, reinforcing the importance of a multidisciplinary approach for these patients.

Accuracy of endoscopic ultrasound in gastric adenocarcinoma patient selection for neoadjuvant therapy.

Background: Recent studies demonstrated the positive impact of neoadjuvant treatment in locally advanced gastric cancer. Objective: To assess the accuracy of endoscopic ultrasound (EUS) in the selection of patients with gastric adenocarcinoma for neoadjuvant therapy (T ≥ 2 and/or N+). Methods: Retrospective analysis of patients with an anatomopathological diagnosis of gastric adenocarcinoma between January 2011 and June 2017, who had EUS for staging and underwent surgery as a first therapeutic attempt. The concordance (k) and accuracy (area under the curve (AUC)) of EUS for T ≥ 2 and/or N+ were assessed using the anatomopathological staging of the resected surgical specimen as the gold standard. Results: The final sample included 152 patients (66.4% male, 67.1 ± 12.2 years). The concordance, accuracy, sensitivity and specificity of the EUS for T ≥ 2 and/or N+ were 0.72, 0.86 ± 0.03, 88.5% and 83.1%, respectively. The results were higher in proximal (k = 0.93, AUC = 0.96 ± 0.05, sensitivity (S) = 99.0% and specificity (E) = 90.9%) compared with distal lesions (k = 0.67, AUC = 0.84 ± 0.04, S = 85.7% and E = 81.5%), and in intestinal subtype (k = 0.77, AUC = 0.88 ± 0.04, S = 92.6% and E = 84.1%) compared with diffuse (k = 0.58, AUC = 0.79 ± 0.10, S = 85.0% and E = 72.7%) or mixed-subtype tumours (k = 0.65, AUC = 0.84 ± 0.10, S = 76.9% and E = 90.0%). Conclusion: In one of the largest series of patients, we showed that EUS has overall high agreement and accuracy in the selection of patients with gastric adenocarcinoma for neoadjuvant therapy, although the agreement and accuracy are greater for proximal and intestinal lesions.

Advanced Polymer Flocculants for Solid-Liquid Separation in Oil Sands Tailings.

The generation of tailings as a by product of the bitumen extraction process is one of the largest environmental footprints of oil sands operations. Most of the tailings treatment technologies use polymer flocculants to induce solid-liquid separation. However, due to the complex composition of tailings, conventional flocculants cannot reach the same performance achieved in other wastewater treatments. Over the last couple of decades, the oil sands industry has used acrylamide-based flocculants to treat tailings, achieving major progress in process optimization and integration with mechanical operations, but they still could not reach the required land reclamation targets. Over the last 5 years, the group designed, synthesized, and tested several novel polymer flocculants tailored for oil sands tailings treatment. This feature article communicates recent developments in these innovative polymers. The article first provides a background on tailings generation and treatment, followed by the description of advanced polymer flocculants categorized according to their microstructures such as linear, branched, and graft. The other tailings remediation technologies and one of the initial works on modeling of tailings flocculation is discussed.

Polymer reaction engineering tools to design multifunctional polymer flocculants.

A series of multifunctional terpolymers, poly(N-isopropyl acrylamide/2-(methacryloyloxy) ethyl trimethyl ammonium chloride/N-tert-butylacrylamide) [P(NIPAM-MATMAC-BAAM)], were designed to flocculate and dewater oil sands mature fine tailings (MFT). The hydrophobic BAAM comonomer helped in expelling water from the sediments, while the cationic MATMAC comonomer promoted the charge neutralization of negatively charged particles suspended in MFT. The chemical composition distributions of these terpolymers were designed based on the knowledge of the reactivity ratios of all comonomers, instead of by trial and error, as usually done for most polymer flocculants. The binary reactivity ratios of the comonomers were estimated by synthesizing the binary copolymers with various mole fractions of each comonomer in the feed and experimentally measuring the corresponding fraction of comonomer in the copolymers. Polymer reaction engineering tools were used to minimize compositional drift and guarantee the synthesis of terpolymers with narrow chemical composition distributions suitable for MFT dewatering. Focused beam reflectance measurement (FBRM) experiments showed that terpolymers promoted the formation of large MFT flocs (120 µm). The initial settling rate decreased with the increase in flocculant hydrophobicity, likely because the hydrophobic terpolymer segments did not take part in the bridging of the MFT particles. In contrast, the sediment dewaterability increased with the increase in terpolymer hydrophobicity. This study provides guidelines to design a polymer flocculant from first principles and demonstrates the potential of using hydrophobically modified cationic polymers to flocculate MFT effectively.

Quantifying the effect of polyacrylamide dosage, Na+ and Ca2+ concentrations, and clay particle size on the flocculation of mature fine tailings with robust statistical methods.

Polymer-driven flocculation and dewatering of mature fine tailings (MFT) is critical to improve their consolidation. MFT flocculation and dewatering depends on the size of the suspended clay particles, and on the composition and properties of the liquid in which they are dispersed. The effect of water chemistry on the polymer-particle dynamics is nontrivial, particularly for non-spherical, polydisperse particles such as natural clays. In this study, we used a response surface methodology to systematically assess the impact of Na+ and Ca2+ concentration and anionic polyacrylamide dosage in the flocculation and dewatering of MFT. We observed a beneficial synergistic effect between Ca2+ concentration and polyacrylamide dosage, although excess of Ca2+ may reduce polyacrylamide activity. In addition, we investigated the impact of clay particle size on MFT flocculation. Polyacrylamide did not flocculate MFT fractions where the fine clay particles (<2 µm) represented most of the population. Good settling, however, was observed when fine silt particles (from 2 to 44 µm) were present, indicating that the presence and accumulation of larger/heavier particles on the polymer-induced flocs is crucial to form aggregates that readily settle under gravity. The insights gained from this study can contribute to more efficient use of flocculants, more effective use of cations, and better understanding of the impact of particles size in MFT flocculation.

Enhanced Flocculation of Oil Sands Mature Fine Tailings Using Hydrophobically Modified Polyacrylamide Copolymers.

Hydrophobically modified acrylamide copolymers dewater oil sands tailings more effectively than anionic polyacrylamide, but the root causes for this enhanced performance have not been investigated systematically. Polyacrylamide-poly(ethylene oxide methyl ether methacrylate) copolymers with different comonomer compositions, hydrophobic chain lengths, and molecular weights to map out these effects systematically are synthetized. Through a statistical design of experiments, it is found out that all three variables above significantly affected flocculation performance and that certain combinations achieve optimal results. The effect of centrifugation on the flocculation and dewatering performance of these polymers is also investigated.