Stability constants of complexes of metal ions with peatsoil humic acids under non-acid-conditions

Stability constants of complexes of four divalent metal ions viz. Cu2+, Pb2+,Mg2+ and Cd2+ with humic acids (HA) were determined by potentiometric titration of humic acids with the corresponding salt of the divalent metals in aqueous media under non-acid-condition. The log K (logarithm of the stability constant) ranged from 1.0942 to 2.7471 for metal-humic acid complexes were determined using point-wise computational method. The order of stability constants were obtained as follows: Cu >Pb> Cd > Mg for metal -HA complexes respectively, indicating a higher degree of complexation with Cu metal ion.

THE EFFECT OF LACTIC ACID AND ARTIFICIAL SALIVA SOLUTION IMMERSION TO THE RELEASE OF CALCIUM IONS ON BIOACTIVE RESIN

Background: Bioactive resin can release calcium ions when contact with solution media, even in acid condition. In the oral cavity, pH may change into acid condition due to the metabolic results of Streptococcus mutans. The bacteria metabolize carbohydrates into organic acids, one of which is lactic acid. Purpose: Analyze the effect of lactic acid solution and artificial saliva on the number of the release of calcium ions of bioactive resin. Methods: Forty-two specimens (diameter 15 mm x thickness 1 mm; n= 7/group fabricated with Activa™ Bioactive Restorative (Pulpdent). The specimens that meet the criteria were divided into 6 groups. The specimen was immersed for 1 and 7 days in the incubator at 37oC. The number of calcium ion release is measured using titration method. Results: Two Way Anova test and Post Hoc Bonferonni test showed there were significant differences among all group for lactic acid 1 day (4.040 ± 0.360) µg, artificial saliva 1 day (0.640 ± 0.338) µg, distilled water 1 day (1.040 ± 0.504) µg, lactic acid 7 days (5.400 ± 0.312), artificial saliva 7 days (1.640 ± 0.215) µg, distilled water 7 days (3.520± 0.356 µg). Conclusion: There was an influence of lactic acid and artificial saliva on the number of calcium ion releases of bioactive resin. Immersion of bioactive resin in the lactic acid solution increase the calcium ion releases and artificial saliva decrease the calcium ion release compared to distilled water. Keywords: artificial saliva, bioactive resin, calcium ion release, lactic acid

Antimony Immobilization in Primary Explosives Contaminated Soils by Fe-Al Based Amendments

The soil in primary explosives sites have been contaminated by high concentrations of antimony(Sb) and co-occurring heavy metals (Cu and Zn), but which is largely overlooked and neglected. In this study, we investigated the concentrations and species of Sb and studied the effect of Fe based, Fe-Al based sorbents combined application on the mobility of Sb and co-occurring metals. The content of Sb in soil samples was from 26.7 to 4255.0 mg/kg, occurring predominantly as Sb(V) (65.57 ~ 95.46%). In batch experiments, FeSO4 showed ideal sorption of Sb (up to 97% sorption with 10% FeSO4·7H2O), while sorption rates of 10% Fe0 and 10% goethite were 72% and 41% respectively. However, Fe-based sorbents enhanced the mobility of co-occurring Cu and Zn in varying levels, especially FeSO4·7H2O. Al(OH)3 was necessary to prevent mobilization of Cu and Zn. In this study, 5% FeSO4·7H2O and 4% Al(OH)3 mixed with soil was the optimal choice to solve this problem with stabilization effect of Sb, Zn, Cu being 94.6%、74.2% and 82.2% respectively. Column tests spiked with 5% FeSO4·7H2O and 4% Al(OH)3 showed significant retention of Sb (85.85%), Zn (83.9%), Cu (94.8%). pH regulated results indicated that acid condition was more beneficial for retention of Sb than alkaline condition. However, there was no significant difference between sets of acidification and sets without pH regulation. Overall, the experimental results showed that 5% FeSO4·7H2O + 4% Al(OH)3 without pH regulation could be effective for the stabilization of Sb and co-occurring metals in primary explosives soils.

Role of Organic and Eco-Friendly Inhibitors on the Corrosion Mitigation of Steel in Acidic Environments—A State-of-Art Review

Steel has versatile application in chemical, structure and construction industries owing to its mechanical properties. However, it is susceptible to corrosion in acid environments. Thus, it requires to protect the steel from corrosion. Different types of corrosion resistance steel, coatings and inhibitors are developed to mitigate the corrosion, but, inhibitor is the best remedies to control the corrosion of steel in acid condition. Moreover, organic and green inhibitors used in acid condition for descaling, acid pickling, pipelines, boiler tubes and oil-wells. Organic inhibitors reduce the dissolution of steel in acid but, it is hazardous, expensive and needs expertise to synthesize the inhibitor. Therefore, there is utmost required to study and compile the latest research about the eco-friendly corrosion inhibitors, which showed more than 90% corrosion inhibition efficiency. In the present study, I have reviewed the state-of-arts, and compile the latest development in organic and eco-friendly corrosion inhibitor used in acid environment as well as suggested about the future scope and role of green inhibitor for sustainable society, which is economical, less hazardous and readily available from the natural sources.

A gastric acid condition enhances the microbial killing effect of ethanol

Tolerance to extremely low pH (< pH 3) is a crucial strategy that enables microorganisms to survive in the human stomach cavity. We found that the killing effect of ethanol on dormant cysts of soil protist Colpoda cucullus, and pathogenic bacteria such as Klebsiella pneumoniae and enterohemorrhagic Escherichia coli O157 was enhanced under stomach acid's low pH condition. This result suggests that gastric-acid-tolerant microorganisms can be partly killed by drinking alcoholic beverages during meals. Keywords: Acid-tolerant microorganisms, ethanol, bactericidal effect.

A comparative study on removal of the dye wastewaters by nascent state manganese dioxide and ferric hydroxide under acid condition

Nascent state manganese dioxide (NSMD) or ferric hydroxide (NSFH) is the main intermediate during potassium permanganate or Fenton oxidation process, respectively, which plays an important role on the removal of...