Search Results (7)

Urban wastewater (UWW) and landfill leachate (LL) co-treatment using membrane bioreactors (MBRs) is a valuable method for managing LL in cities. Coagulants can enhance the filterability of mixed liquor (ML), but the assessment of fouling is still needed. This research aimed to investigate the effects of co-treating synthetic wastewater (SWW) and real LL on an MBR, as well as the impact of adding poly-aluminum chloride (PACl) and Tanfloc SG. Cell-ultrafiltration experiments were conducted with four different feeds: synthetic wastewater, co-treatment with LL (20% v/v), and co-treatment with the addition of 30 mg L⁻¹ coagulants (either PACl or Tanfloc). Co-treatment aggravated flux loss and reduced the recovery rate; however, Tanfloc and PACl improved recovery after cleaning (by 11% and 9%, respectively). Co-treatment also increased cake and irrecoverable/irremovable inorganic resistances, though coagulants reduced the latter, despite a lower fit of the Hermia models during the first hour of filtration. Co-treatment reduced the removal efficiencies of almost all pollutants analyzed, with the most significant impacts observed on the organic fraction. Coagulants, particularly Tanfloc, enhanced overall performance by improving flux recovery and reducing irreversibility, thus benefiting membrane lifespan. In conclusion, Tanfloc addition yielded the best results in terms of filterability and pollutant removal. Full article

Bacterial infections are a common mode of failure for medical implants. This study aims to develop antibacterial polyelectrolyte multilayer (PEM) coatings that contain a plant-derived condensed tannin polymer (Tanfloc, TAN) with inherent antimicrobial activity. Tanfloc is amphoteric, and herein we show that it can be used as either a polyanion or a polycation in PEMs, thereby expanding the possibility of its use in PEM coatings. PEMs are ordinarily formed using a polycation and a polyanion, in which the functional (ionic) groups of the two polymers are complexed to each other. However, using the amphoteric polymer Tanfloc with weakly basic amine and weakly acidic catechol and pyrogallol groups enables PEM formation using only one or the other of its functional groups, leaving the other functional group available to impart antibacterial activity. This work demonstrates Tanfloc-containing PEMs using multiple counter-polyelectrolytes including three polyanionic glycosaminoglycans of varying charge density, and the polycations N,N,N-trimethyl chitosan and polyethyleneimine. The layer-by-layer (LbL) assembly of PEMs was monitored using in situ Fourier-transform surface plasmon resonance (FT-SPR), confirming a stable LbL assembly. X-ray photoelectron spectroscopy (XPS) was used to evaluate surface chemistry, and atomic force microscopy (AFM) was used to determine the surface roughness. The LDH release levels from cells cultured on the Tanfloc-containing PEMs were not statistically different from those on the negative control (p > 0.05), confirming their non-cytotoxicity, while exhibiting remarkable antiadhesive and bactericidal properties against Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus), respectively. The antibacterial effects were attributed to electrostatic interactions and Tanfloc’s polyphenolic nature. This work underscores the potential of Tanfloc as a versatile biomaterial for combating infections on surfaces. Full article

From the rupture of the Fundão dam in Mariana–MG, there are tailings still present at the bottom of the plant that must be recovered. The flocculation followed by sedimentation operation can be applied as a unit operation in this recovering process. Instead of using conventional inorganic coagulants, bio-based coagulants offer some advantages, due to their low toxicity and biodegradability. Nonetheless, the use of bio-based coagulants in the mining industry is not established yet, due to the complex parameters that must be taken in consideration. This study analyzes the influence of the pH and flocculant concentration, which are the variables of the 2² full factorial design. The pH value for the batch sedimentation process was defined ranging from 5 to 9. Tanfloc, a tannin-based coagulant, was used as a coagulant agent. The results indicate a strong dependence on the coagulant concentration, and a recommended 15 g/L dosage with pH varying from 6 to 8. From batch sedimentation, it was possible to determine an exponential model for the sedimentation with an excellent fitting (R² = 0.997). The sedimentation efficiency calculated is 65.6%. These results confirm the potential use of bio-based materials in mining tailing treatments. In addition, they can be used in equipment sizing and simulations of the sedimentation operation. Full article

The development of composites with antibacterial activity represents an important strategy to avoid side effects such as increasing bacterial resistance to antibiotics. In particular, the green synthesis of metal nanoparticles avoids the use of hazardous chemical compounds and introduces the intrinsic beneficial properties of plant-derived compounds. Herein, the reduction of gold salt into metal nanoparticles was provided by the action of a cationic polymer derived from tannin (Tanfloc^®). Comparative activity of antibacterial agents (pure Tanfloc and Au NPs—Tanfloc) at different concentrations were evaluated in terms of the antibiofilm activity, kill-time assays and inhibition haloes confirming the antibacterial activity of the Tanfloc that is reinforced by the incorporation of reduced gold nanoparticles, resulting in the complete elimination of S. aureus from an initial concentration of 10⁸ CFU/mL after 120 min of reaction of Au NPs + Tanfloc solution in association with strong inhibition of the biofilm formation attributed to the Tanfloc. Full article

Microalgae have a lot of potential as a source of several compounds of interest to various industries. However, developing a sustainable and efficient harvesting process on a large scale is still a major challenge. This is particularly a problem when the production of low-value products is intended. Chemical flocculation, followed by sedimentation, is seen as an alternative method to improve the energetic and economic balance of the harvesting step. In this study, inorganic (aluminum sulfate, ferric sulfate, ferric chloride) and organic (Zetag 8185, chitosan, Tanfloc SG) flocculants were tested to harvest Chlorella vulgaris in batch mode. Preliminary assays were conducted to determine the minimum dosages of each flocculant that generates primary flocs at different pH. Except for chitosan, the organic flocculants required small dosages to initiate floc formation. Additional studies were performed for the flocculants with a better performance in the preliminary assays. Zetag 8185 had the best results, reaching 98.8% and 97.9% efficiencies with dosages of 50 and 100 mg L⁻¹, respectively. Lastly, a 2⁴ full factorial design experiment was performed to determine the effects of the flocculant dosage, settling time, and mixing time on the Zetag 8185 harvesting efficiency. The harvesting efficiency of C. vulgaris was optimal at a dosage of 100 mg L⁻¹ and 3 min of rapid mixing. Full article

Optimization of coagulant dosage and pH to reduce the turbidity and chemical oxygen demand (COD) of synthetic dairy wastewater (SDW) was investigated using a full factorial design (FFD) and full factorial design with center point (FFDCP). Two organic coagulants, polyacrylamide (PAM) and Tanfloc were used. The optimal values of coagulant dosage and pH were determined using a multiple response optimization tool and desirability function. The results obtained revealed that the optimum condition for removing turbidity and COD were at pH 5.0 using 50 mg L⁻¹ of coagulant. The same optimum point was obtained in both experimental designs, indicating a good agreement between them. In optimum conditions, the expected removal of turbidity was above 98% with PAM and above 95% with Tanfloc. The estimated COD removal was above 72% with PAM and above 65% with Tanfloc. The addition of center points with replicates in the factorial design allowed to obtain the estimate of the experimental error with a smaller number of runs, allowing to save time and cost of the experimental tests. Moreover, the addition of center points did not affect the estimates of the factorial effects and it was possible to verify the effect of curvature, allowing obtaining information about the factors at intermediate levels. Full article

Polymeric nanofiber membranes of polyvinyl chloride (PVC) blended with polyvinylpyrrolidone (PVP) were fabricated using an electrospinning process at different conditions and used for the filtration of three different liquid suspensions to determine the efficiency of the filter membranes. The three liquid suspensions included lake water, abrasive particles from a water jet cutter, and suspended magnetite nanoparticles. The major goal of this research work was to create highly hydrophilic nanofiber membranes and utilize them to filter the suspended liquids at an optimal level of purification (i.e., drinkable level). In order to overcome the fouling/biofouling/blocking problems of the membrane, a coagulation process, which enhances the membrane’s efficiency for removing colloidal particles, was used as a pre-treatment process. Two chemical agents, Tanfloc (organic) and Alum (inorganic), were chosen for the flocculation/coagulation process. The removal efficiency of the suspended particles in the liquids was measured in terms of turbidity, pH, and total dissolved solids (TDS). It was observed that the coagulation/filtration experiments were more efficient at removing turbidity, compared to the direct filtration process performed without any coagulation and filter media. Full article