Study On Sulfuric Acid Pickling Inhibitor Extracted From Bamboo Leaves

In this paper, the environment-friendly sulfuric acid pickling inhibitor was extracted from bamboo leaves. By comparing a variety of extraction methods of bamboo leaves, the effect of different extraction method on inhibition efficiency of extract was investigated. By weight-loss method, electrochemical method and surface analysis method, the corrosion performance and mechanism of the bamboo leaves extract was studied, and the same research has been taken on its mixtures with potassium iodide. By separation, the effective corrosion inhibition composition of bamboo leaves extract was preliminarily investigated. Finally, By sequential extraction, the comprehensive utilization of bamboo leaves was discussed.The study on extraction methods showed that: the most economic and applicable method of exacting inhibitor from bamboo leaves by acid soaking. The optimum condition of extracting was as follows: bamboo leaves were soaked by 15% sulfuric acid for 5h, preparing solution of the ratio of bamboo mass to 15% sulfuric acid volume was 1g:10mL, and inhibition efficiency was up to 96%.The study on bamboo leaves extract showed that: (1) bamboo leaves extract can comparably inhibit the cathodic reaction and anodic reaction of carbon steel in sulfuric acid solution, so it was a mixed type inhibitor, and its mechanism was coverage effects. (2) with increase of the bamboo leaves extract concentration, inhibition efficiency increased, desorption potential had a positive shift; with increase of the temperature, inhibition efficiency decreased, desorption potential had a negative shift. (3) the absorption of bamboo leaves extract on the surface of carbon steel was in line with El-Awady dynamic model and Flory-Huggins adsorption isotherm equation. (4) surface analysis found that: some components of bamboo leaves extract occurred chemisorption on the electrode surface, the corrosion of carbon steel was inhibited in sulfuric acid. after soaked in sulfuric acid containing bamboo leaves extract, the enrichment phenomenon of copper appear on the carbon steel surface.The synergy research showed that: (1) the significant synergistic effect was existed between bamboo leaves extract and 0.001mol/L potassium iodide; the inhibition efficiency was up to 98% after synergy. And the synergistic inhibitor can comparably inhibit the cathodic reaction and anodic reaction of carbon steel in sulfuric acid solution, so it was a mixed type inhibitor and its mechanism was coverage effect. (2) after bamboo leaves extract mixed with potassium iodide, the desorption potential positively shifted and corrosion potential negatively shifted, so the inhibitor region was increased and the adsorption stability of inhibitor was improved. (3) the inhibition efficiency was increased with increase of concentration, and the variety was little with increase of temperature. (4) the absorption model of bamboo leaves and potassium iodide on the carbon steel surface was mainly staggered absorption, and the absorption on the surface of carbon steel was in line with El-Awady dynamic model and Flory-Huggins adsorption isotherm equation; (5) surface analysis found that: the addition of potassium iodide promoted adsorption of the effective corrosion inhibition composition of bamboo leaves extract on the electrode surface, and the corrosion of carbon steel was significantly inhibited in sulfuric acid.The three isolates were got by preliminary separation. The electrochemical tests showed that the corrosion inhibition of bamboo leaves were mainly attibute to isolates 2 and isolates 3, but the corrosion performance of isolates 1 was very bad, and synergistic effect was existed between isolates 2 and isolates 3. Combined with previous experimental results, a priliminarily conclusion can be drown that the effective corrosion inhibition composition of bamboo leaves extract included organic acids and their salts, anthraquinones, amino acids and alkaloids and the synergistic effect did exist between the effective components. But all of these need further confirm.By comprehensive extraction, bamboo leaves of polysaccharides, chlorophyll, flavonoids and sulfuric acid extract were got. Polysaccharide extraction rate was 1.27%, chlorophyll extraction rate was 3.94%, flavone extraction rate was 0.24%, the inhibition efficiency of sulfuric acid extract was 89.55%, and sulfuric acid extract mixed with 0.001mol/L potassium iodide made the inhibition efficiency up to 97.71%.