Preparation And Mechanism Study Of Environment-friendly Scale And Corrosion Inhibitor

The circulating cooling water has been extensively applied in various industrial processes.However,scale and corrosion have destroyed the normal operation of the cooling water system.The cooling water in the process of continuous circulation,which increases the salt content of the cooling water and tends to scale.Moreover,when the equipment is used for a long time,the surface is easy to cause corrosion.The problem of scale and corrosion has severely affected industrial production,causing issues such as lower efficiency of equipment,a substantial amount of economic loss,and unsafe production.The addition of inhibitor to the environment is regarded as the most straightforward and effective method.At present,the inhibitor used in industry can cause secondary pollution to the environment,which restricts their practical applications in industrial settings.Therefore,a great deal of attention has been brought to the development of non-phosphorus,efficient,and“green”scale inhibitor.In this study,polyaspartic acid（PASP）,a typical representative of green inhibitor,was used as the main raw material to prepare five green inhibitors with excellent performance.（1）The intermediate polysuccinimide（PSI）of PASP was synthesized using maleic anhydride（MA）and urea as the main raw materials,and then PASP was synthesized by ring-opening reaction of PSI under alkaline conditions.The dehydration condensation reaction between PASP and graphene oxide（GO）was taken advantage of to synthesize a novel and highly efficient PASP/GO.PASP/OS was successfully synthesized by dehydration condensation reaction using PSI and oxidized starch（OS）as raw materials.From the perspective of chemical structures and morphologies,the successful synthesis of PASP/GO and PASP/OS was demonstrated by Fourier transform infrared spectroscopy（FTIR）,proton nuclear magnetic resonance（¹H NMR）,and scanning electron microscopy（SEM）.The thermal stability was analyzed by thermogravimetric（TG）,and the surface area and pore size of PASP/GO and PASP/OS were determined with the assistance of an aperture and specific surface area analyzer（BET）.Then,a static scale inhibition experiment was conducted to study the inhibition efficiency of PASP/GO and PASP/OS against Ca CO₃ and Ca SO₄,which completely inhibited Ca CO₃ and Ca SO₄ at 8 mg/L.The morphology and crystal structure were characterized by SEM and X-ray diffraction（XRD）.Besides,PASP/GO and PASP/OS have excellent ability to disperse Fe₂O₃.The performance of PASP/GO is slightly better than that of PASP/OS by comparison.（2）PASP/CMCS and PASP/GA were synthesized by ring-opening reaction of carboxymethyl chitosan（CMCS）and glycyrrhizic acid（GA）with PSI under alkaline conditions.The composites were characterized by FTIR,¹H NMR,SEM,TG,and BET.The ability of PASP/CMCS and PASP/GA to protect carbon steel was investigated by weight loss,polarization curve,and electrochemical impedance spectroscopy（EIS）.The corrosion inhibition performance tended to be stable at 80 mg/L,and the maximum corrosion inhibition efficiency of PASP/CMCS and PASP/GA was 82.2%and 77.2%,respectively（weight loss method）.The polarization curves showed that PASP/CMCS and PASP/GA were mixed-type corrosion inhibitors.The corrosion degree on the surface of carbon steel was analyzed by SEM,which showed that the PASP/CMCS and PASP/GA could protect carbon steel.The performance of PASP/CMCS is better than that of PASP/GA by comparison.（3）Based on the above screening,a composite material with both scale inhibition and corrosion inhibition was synthesized.GO was activated by a mixture of soluble 1-（3-Dimethylaminopropyl）-3-ethylcarbodiimide hydrochloride（EDC）and N-Hydroxy succinimide（NHS）,and then reacted with PASP/CMCS by dehydration condensation to form PASP/CMCS/GO.PASP/CMCS/GO was characterized by FTIR,SEM,TG,and BET.The ability of PASP/CMCS/GO to inhibit Ca CO₃ and Ca SO₄,disperse Fe₂O₃ and protect carbon steel was investigated.The results showed that PASP/CMCS/GO was superior to binary composite materials in inhibition ability.Besides,combined with the theoretical calculation method,the performance and mechanism of scale and corrosion inhibition were further explained.