Bucharest) ♦ 61♦ Nr

The removal of kaolin fine particles from water by precipitation with polyelectrolyte and surfactant complex of polyacrylamide and hexadecyl trimethyl ammonium bromide (HTAB) Keywords: kaolin, polyacrylamide, hexadecyl trimethyl ammonium bromide (HTAB) The coagulation-flocculation process is an important part of surface water treatment. It has an impact on the reliability of operation and water quality. Coagulationflocculation process is influenced by raw water physical, chemical and bacteriological parameters, treatment device structures, as well as coagulant types and dosages. Colloids of water are very fine particles, typically ranging from 10 nm to 10 μm. There are two types of colloids: hydrophilic colloids which are unstable and hydrophilic colloids that are stable. Generally, the solid particles from surface water have negative electrical charges, are unstable and can be easily destabilized. The magnitude of the zeta potential ζ is usually used to indicate colloidal particle stability. Coagulation is the destabilization of colloidal particles by the addition of a chemical reagent. The optimum dosage of coagulant corresponds to ζ which is near zero. A further increase in coagulant dose will cause restabilization of the particles due to charge reversal on the colloids [1]. The control of pH is an essential aspect of coagulation and flock formation and an optimum pH exists for each system -the mechanism of double-layer compression relying on compressing the diffuse layer surrounding a colloid when an electrolyte is added and so the ζ decreases, -the mechanism of adsorption and charge neutralization: coagulants with an opposite charge are used, they are adsorbed on the colloidal particles and neutralize surface charge; -the mechanism of enmeshment by a precipitate consisting in adding of chemical compounds which precipitate and physically entrap the suspended colloidal particles as they settle; e-mail: [email protected] -the mechanism of inter-particle bridging: synthetic polymeric compounds having large molecular sizes and multiple electrical charges along the molecular chain of carbon atoms are applied. Flocculation is the agglomeration of destabilized particles.There are three major mechanisms of flocculation -perikinetic flocculation is the aggregation of particles caused by random Brownian motion and it occurs when the most particles are less than 1 μm in diameter; -orthokinetic flocculation is the aggregation of particles caused by induced energy in the fluid and it occurs when both particles are larger than 1 μm in diameter and similar in size; -differential settling is caused by different settling velocities of particles and it occurs when at least one of the particles is larger than 10 μm in diameter and the other is significantly different in size When the polymer is used as coagulation-flocculation agent, the major mechanism includes both adsorption and inter-particle bridgin

Experimental Study on the Corrosion of Carbon Steel and Aluminum Alloy in Firefighting Protein Foam Concentrates

The corrosion of mild steel and Al alloy in Fomtec P 6% and 6% P Profoam 806 protein-based foam concentrates was investigated. Weight-loss data for steel showed corrosion penetration of 0.745 mipy in Fomtec and 2.269 mipy in Profoam, whereas for Al alloy the penetration levels were 0.474 and 1.093 mipy, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy allowed characterization of the metallic surface covered or free from corrosion products. Values of corrosion potential, corrosion current density and corrosion penetration were calculated by using potentiodynamic polarization curves. Electrochemical impedance spectra illustrated the change in polarization resistance during anodic polarization. Data obtained by accelerated electrochemical methods confirm the greater aggressiveness of the Profoam concentrate compared to Fomtec concentrate

Bucureºti) ♦ 60♦ Nr

Carbon disk electrodes with film of poly ethylenediamine tetra-N-(3-pyrrole-1-yl