Determination of the critical concentration of partially hydrolyzed polyacrylamide by potentiometry in an acidic medium

Abstract

The literature presents different methods for quantifying and characterizing partially hydrolyzed polyacrylamide (HPAM) in solution. However, only a few of these are suitable for determining the critical overlap concentration (C \ ). The evaluation of C \ is important for describing the transition from the dilute to the semidilute regime, that is, when the solution depicts a characteristic viscosity at concentrations above C \ . This article describes the determination of C \ for HPAM in solution by potentiometry. The molecular weight, degree of hydrolysis, and polymerization degree are determined by mathematical manipulation of the constant of formation of aggregates, which is based on the law of mass action. The potentiometric curves were initially linear; asymptotic behavior followed. The inflection point was determined by the intersection, and the resulting equation of mathematical development statistically satisfied the experimental data and described the number of moles of monomers, the equilibrium constant for the formation of the aggregate, C \ , and the acidity constant of the polymer. The results for C \ , the degree of copolymerization, and the molecular weight proved that this method is a good alternative for the characterization of polymers with ionizable monomers and that are soluble in water.

Visualization of polymer relaxation in viscoelastic turbulent micro-channel flow

“…The conformations of the phPAA-FITC molecules were dynamically tracked under epi-fluorescence illumination at De = 41.46 (1 ml/h) and 414.6 (10 ml/h). Here, the observed phPAA-FITC molecules were polymer aggregates; this occurs naturally even at dilute concentrations 21 22 . Details of the molecular imaging setup have been included in the Methods section.…”

“…32 × 22 μm (β/α = 1.5), which was obtained by measuring ≈1000 polymer molecules under static conditions. It should be noted that the size of a single PAA molecule 29 (5 × 10 6 g/mol) is ≈1–2 μm, and the larger molecular size observed is the result of molecular aggregation 21 22 . Supplementary Table S2 shows the size distribution of the molecules, which has been subcategorized into 100 μm 2 incremental size ranges.…”

Enhanced efficiencies of sludge dewatering and domestic wastewater treatment by using the bioflocculant from rice stover

“…(b), absolute value of the sludge's zeta potential was decreased rapidly, when the bioflocculant dose was adjusted in the range of 0–18 mg/L, and the downtrend of the absolute value became slow when the bioflocculant was increased continually to 24 mg/L. The decline was due to the electrical neutralisation between the positively charged bioflocculant and the negatively charged sludge particles, and thus reducing the electrostatic repulsion between sludge particles and compressing the particles’ electric double layer, thus far, the loose sludge particles became larger and more stable, which promote the sludge sedimentation (Gomes & Costa, ).…”