Active Ingredients Extracted From Excess Sewage Sludge And Their Application In The Process Of Cleaner Pickling

Excess sewage sludge (ESS) is a by-product of urban sewage treatment plant operating, it will cause secondary pollution without proper disposal. However, the ESS is considered as a kind of resources because the characteristics of the composition. The microorganisms of excess sludge contain large amounts of amino acids material for recycling. The amino acid materials are used as a corrosion inhibitor with the advantages of high efficiency, easy biodegradation and environmental friendly, It gets a kind of useful resources while reduce sludge and solve the excessive corrosion in the steel pickling process.if we can extract the amino acid as a corrosion inhibitor.The purpose of this study is to extrat the active ingredients of the excess sewage sludge as a pickling corrosion inhibitor. The first step of the whole experiement is to optimize the conditions and influencing factors of extracting. The second step is to employ the Fourier infrared spectrum (FTIR) and Ninhydrin staining method for characterization of the amino acid of the extract.The third step is to test the corrosion performance of extract for the A3carbon steel in the HC1by weight-loss, electrochemical polarization curve and scanning electron microscopy (SEM) methods, then, the inhibition mechanism is studied by adsorption thermodynamics and kinetics behavior. In order to offer theoretical basis to realize sludge reduction and resource recovery, the ultimate aim is to explore the high-added value utilization way of excess sludge resource.Research results show that the ultrasonic assisted HCl-hydrothermal method is an effective and fast approachfor extraction of organic and amino acids. The organic extractionefficiencyis87.53%while the sludge hydrolyzed18hat the100±0.5℃, the volume ratio of HCl and sludge is10ml:100ml, and sludge water content is99±0.2%. On the other hand, the concentration of hydrolysate is1.234g/L while the sludge hydrolyzed18hat the100±0.5℃, the volume ratio of HCl and sludge is8ml:100ml, and sludge water content is96±0.2%.And the the Fourier infrared spectrum (FTIR) and Ninhydrin staining method result indicate that the extrat contain the amino acids compounds. The weight-loss and SEM results show that the extract is a good corrosion ibhibitor for A3carbon in HCl, and the inhibition efficiency increases with the extract concentration increasing in the HCl, meanwhile, decrease with the temperature decreasing.The best corrosion rate for the matrix carbon steel is over93.0%at30±0.5℃while the extract volume is15ml in the100ml immersion solution (amino acid concentration is0.186g/L). The corrosion rate for the carbon steel with oxide layer and natural rust is82.93%and89.77%at30±0.5℃, respectively, while the extract volume is20ml in the100ml immersion solution (amino acid concentration is0.248g/L). On the other hand, the electrochemical experimental results are basically identical with weight-loss method. The polarization curve measurements also indicated that the extracts were a mixed-type inhibitor, which can restrict simultaneously the hydrogen evolution on the cathode and the metal dissolution on the anode for matrix carbon steel.The adsorption of extract on the A3carbon surface follows the amended Langmuir adsorption isotherm equation, The values of←G0, located in the range from-40to-20kJ·mol-1, reveal that the process on the surface is a combined physical-chemical adsorption.The negative value of⊿H0implies the adsorption of extracts on the surface is exothermic, which means the adsorption process is more likely to occur under lower temperature. The values of⊿S0are positive, which demonstrates the replacing process leads to the increasing of the disorder of the whole system.The apparent activation energy (Ea) and lnA increases with the concentration of extracts increasing, which implies the mechanism of corrosion inhibition lies in the increasing of energy barrier for a corrosion reaction.