Portugaliae
Electrochimica Acta

ATK was investigated to ascertain its IE(%) on ASTM A36 MS corrosion in a HCl medium. This was possible through the use of WL, Td, Tm, PDP, EIS and SEM techniques. It was seen from all experimental results that, through adsorption onto the MS surface, ATK mitigated active corrosion sites. CR was seen to decrease with higher inhibitor Ct from 197.6 to 19.3 mg/hr-1/cm2. IE(%) of ATK, which rose from 50 to 90.2%, with corresponding increased Ct, from 150 to 750 ppm, was better by adding PPQ to it than ATS. An increase in Rct, up from 346 to 1153 Ω/cm2, and a decrease in icorr, from 312.2 to 64.4 mA, were seen, with higher Ct of ATK, which indicated reduced anodic dissolution and better CI. A mixed type inhibition was deduced from Tafel slopes of PDP results. A physical adsorption mechanism was proposed, while, in Td terms, ATK exhibited a stable and spontaneous reaction. Keywords: ASTM A36 MS; ATK; ATS; corrosion; computational and electrochemical studies; EIS; PDP; PPQ: SEM.

IE(%) of SCLAE on CR of CS immersed in 1 N HCl was herein assessed by WL method. The former increased and the latter decreased in the solution with higher Ct of SCLAE. The inhibitor blocked MS corrosion active sites, and created a protective layer that covered its surface. Pc constituents of SCLAE allowed the interaction between their hetero atoms and the metal ions from the CS surface, hindering its corrosion. Elc studies were herein used to confirm the formation of a protective layer on the CS surface. They were further reinforced by surface analysis techniques, such as FTIR and SEM. EDAX was used to analyze the elements present on the CS surface, after its immersion in 1 N HCl without and with SCLAE. Ra of polished, corroded and inhibited CS surfaces was analyzed by SEM and AFM. Keywords: AFM, corrosion, CS, EDAX, FTIR, HCl, IE (%), SCLAE, SEM and WL method.

In view of enhanced Pc applications, doped materials have drawn much attention. The present work focused on synthesizing pure and Pd doped WO3 Np, which were used as Pc for MB and RhB aqueous solutions discoloration, under VL, by a unique MWI technique. XRD and TEM studies revealed that Pd dopant did not influence WO3 samples structure and morphology, since they had mono-dispersed spherical forms, with an average diameter of about 50-30 nm. Optical spectra showed a red shift in the absorption edges, with an increase in Ct of Pd from 0 to 10 wt%, which indicates the decrease in Eg of WO3 with Pd doping. Eg was calculated as 3.02, 2.84 and 2.73 eV, for pure and Pd (5 and 10 wt%) doped WO3 samples, respectively. Pc intensity of Pd doped WO3 was significantly higher than that of the pure one. This was due to the recombination of photo-excited electrons and holes. Pc activities of pure and Pd doped WO3 samples were analyzed based on their ability to degrade MB and RhB dyes under VL. Pd doped WO3 showed better Pc degradation, due to an increase in SA, and a decrease in Eg and O vacancies. Keywords: MWI; Pc; Pd; TEM; WO3; VL; XRD.

This study carried out Bg anaerobic Cd. RSM was employed to investigate optimum experimental conditions for Bg yield. Input parameters were PD substrates combination, either with WH or GS. Using six different identical 25 L cylindrical digesters, 6 substrate combinations experimental setups were carried out, for an incubation time of 22 days, under ambient T of 33 °C and pH of 6.7. The setups digesters were: 25% PD:75% WH (1); 50% PD: 50% WH (2); 75% PD:25% WH (3); 25% PD:75% GS (4); 50% PD: 50% GS (5); and 75% PD:25% GS (6). From experimental observations, Bg yield started on day 5, for setups 1, 2, 4 and 5, followed by setup 3 on day 6. Setup 6 was the last digester to produce Bg, on day 7. Setup 2 recorded the highest Bg yield (75 cm3/day), while setup 6 had the lowest value yield (48 cm3/day). Furthermore, additional setups (7 and 8) were carried out for determining Bg characteristics, and evaluating the effect of a pre-activated active slurry on its yields. Optimum Bg yield (75 cm3/day) was attained by 50% PD: 50% WH. This result validates Bg production through substrates Cd, and the employment of optimization tools, in order to obtain ideal process parameters. Furthermore, quadratic model developed by RSM was highly reliable and reproducible, while the predicted values were close to the experimental ones. Keywords: AD; additives; Bg; Cd; optimization; RSM.

This study performed LSV simulation of two-step irreversible electron oxidation with the intermediate (E↓E), which was immobilized on the electrode surface. The response exhibited either one or two peaks, depending on the intermediate stability. The first electron transfer depended on the reactant diffusion, while the second one was a function of the accumulated intermediate. For this reason, the second Ip was higher than the first one, and the single peak split into two peaks, under the influence of an increased SR. Thermodynamic and kinetic parameters influence on the two components of the response were analyzed. Keywords: EE mechanism; intermediate immobilization; kinetic stabilization; two-step electron oxidation; voltammetry.