Preparation Of Natural Corrosion And Scale Inhibitors And Study Of Synergistic Properties

In the field of chemical industry,many reactions need cooling water circulating system to ensure normal reaction temperature and normal chemical production.The equipment of cooling water circulating system is based on the heat exchanger and is generally made of carbon steel,copper or other metal materials.The circulating cooling water system has many problems during long-term operation,such as scaling and corrosion of metal pipes.In industry,in order to prevent and alleviate the above problems occurring,adding scale and corrosion inhibitors is usually the method to solve them.Most of them have good effect on scale and corrosion inhibition,but will result secondary pollution.Recently,with the increasing awareness of environmental protection,it is the inevitable trend to develop environmentally friendly scale and corrosion inhibitors.Many plants contain a large number of organic compounds,which are potential scale and corrosion inhibitors.As natural product,they have a great application prospect because they are non-toxic,biodegradable and have wide sources,low extraction cost.In this paper,active ingredients were extracted from several kinds of plants?such as Ipomoea batatas,Dioscorea opposita,Daucus carota stem and leaf,Raphanus sativus stem and leaf,etc.?.The scale inhibition performance was evaluated by the method of static scale inhibition.The corrosion inhibition performance and synergistic effect was evaluated by the method of weight loss,rotating hanging plate,electrochemistry,and scanning electron microscopy?SEM?,adsorption themodynamics and theoretical calculation are used as assisting means.Finally,the feasibility of industrial application was discussed through pilot-scale dynamic simulation test.The main research contents and results are listed as follows:?1?Wastewater of Sweet Potato Starch Production,Dioscorea opposita,Daucus carota stem and leaf,Raphanus sativus stem and leaf were extracted with water and ethanol as solvents by ultrasound and Soxhlet extraction.Wastewater of Sweet Potato Starch Production extract?IBWE?,Dioscorea opposita water extract?DOWE?and ethanol extract?DOWE?,Daucus carota stem and leaf water extract?DSLWE?and ethanol extract?DSLEE?,Raphanus sativus stem and leaf water extract?RSLWE?and ethanol extract?RSLEE?were obtained.Then the scale and corrosion inhibition performance and synergistic effect were discussed.?2?The static method was conducted to evaluate the scale inhibition of extracts.The research indicated that the extracts had excellent scale inhibition properties.The inhibition efficiency reached 100%against CaSO₄ of DOWE at 0.18 g/L.When the concentration of DSLWE is 0.12 g/L,the efficiency against CaSO₄reached 100%.The inhibition efficiency against CaCO₃ and CaSO₄ reached 100%of RSLWE at 0.40 g/L.The inhibition efficiency against CaCO₃ and CaSO₄ reached more than 95%at 0.40 g/L with RSLEE.The effect of extract on the morphology and crystallinity of scale was studied by SEM and XRD.The lattice of scale was distorted after adding extract,and became fine and dispersible.?3?The corrosion inhibition properties of the extracts were investigated by weight loss,rotating hanging plate and electrochemical methods at different temperatures.The results showed that the inhibition efficiency reached 82.62%when the concentration of RSLWE was 1.50 g/L in the salt solution at 45°C.When DOWE concentration is 0.4 g/L,the corrosion inhibition efficiency reaches 92%in sulfuric acid at25?.When RSLEE concentration is 1.0 g/L,the corrosion inhibition efficiency reaches 96%in hydrochloric acid.When the concentration of DSLWE is 1.0 g/L,the corrosion inhibition efficiency reaches 95%in sulfuric acid at 35?.The electrochemical results showed that the extract was a mixed corrosion inhibitor based on cathode inhibition.According to the thermodynamic parameters,the extracts were absorbed on the surface of carbon steel according to physical and chemical absorption to slow down the corrosion of carbon steel.The contribution of the organics component in the extract to the inhibition is estimated by theoretical calculation.?4?The synergistic properties of PASP/4-AMPY,PESA and ZnSO₄ with RSLES were discussed by orthogonal test in salt solution.The results showed that the optimum concentration ratio?Comp-1?was RSLES 40 mg/L,PESA 40 mg/L,PASP/4-AMPY 15 mg/L and ZnSO₄ 4 mg/L,which the corrosion inhibition efficiency can reach 95.21%.The corrosion inhibition efficiency of Comp-2 is only 77%?PESA:PASP/4-AMPY:ZnSO₄ 40 mg/L:15 mg/L:4 mg/L?.The corrosion inhibition efficiency of Comp-1 can still reach90%,while that of Comp-2 is only 60%at 85?.The synergistic effect of four single agents is very obvious,and their temperature resistance is also improved.?5?The dynamic simulation experiment of combination material was carried out by WKMZ-II device.The annual corrosion rates of Comp-1 and Comp-2 were 0.041 mm/a and 0.096 mm/a,respectively,and the fouling thermal resistance was 0.866×10^-4 m² K/W and 1.356×10^-4 m² K/W,respectively,under the control of three times concentration ratio and the cycle is 15 days.The annual corrosion rate and fouling thermal resistance of Comp-1 have reached national standard(<0.075 mm/a,<3.44×10^-44 m^2.K/W).?6?The biodegradability of Comp-1 and Comp-2 was investigated by aerobic biodegradation method.The degradation efficiency of Comp-1 and Comp-2 were 83%and 81%respectively,showing excellent biodegradability.