Performance and Mechanism of a Composite Scaling鈥揷orrosion
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'HVDOLQDWLRQ Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal Performance and mechanism of a composite scaling–corrosion inhibitor used in seawater: 10-Methylacridinium iodide and sodium citrate ⁎ Weiwei Zhanga, Hui-Jing Lia,b, , Liwei Chena, Jiani Suna, Xingyi Mac, Yunfei Lia, Chao Liua, ⁎ Xu Hana, Boyi Panga, Yan-Chao Wua,b, a School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, PR China b Weihai Institute of Marine Biomedical Industrial Technology, Wendeng District, Weihai 264400, PR China c Department of Chemical & Biological Engineering, Korea University, Seoul 136713, Republic of Korea ARTICLE INFO ABSTRACT Keywords: An environment-friendly scaling–corrosion inhibitor composed of 10-methylacridinium iodide (MAI) and so- Mild steel dium citrate (SC) was developed, whose scale inhibition performance were studied through weight loss, elec- Seawater trochemical techniques, static tests and surface analysis techniques (SEM, SECM, XPS, XRD). The optimum mass Corrosion inhibition ratio of MAI and SC corrosion inhibition was found to be 1:2, and the optimum mass ratio of scale inhibition was Scale inhibition 1:3. The experimental results showed that MAI–SC mixture as mixed-type scaling–corrosion inhibitor with ex- Surface analysis cellent corrosion (ηw = 92.7%) and scale inhibition performance (ηCa = 98.3%). The electrochemical stability of the inhibitor film was investigated by chronoamperometry (CA). SEM and XRD simulations indicated that the MAI–SC mixture inhibitor can distort and disperse the crystal lattice of calcium carbonate without forming scale, and it plays a dominant role in the inhibition of calcite (110) surface growth. The structure-activity relationship between the molecule structure of the MAI–SC mixture and its scale–corrosion inhibition performance was discussed based on the quantum chemistry calculation. 1. Introduction exploited to decrease the difference between desalination water tests and the related practical steel protection. Even so, most of the existing With the fast growth of manufacturing and heavy industries such as scale inhibitors face problems such as non-biodegradability and poor steel, power generation and chemical industry, the demand for fresh scale inhibition performance, which cannot meet the requirements of water in industrial production is increasing, which has increased the industrial application. Besides, in industrial operations, a single type of scarcity of water resources. Committed to alleviating water pressure, corrosion inhibitor is often insufficient to meet actual steel protection seawater is increasingly used in industrial applications, especially in requirements. Accordingly, the combination of corrosion inhibitors cooling systems and desalination plants. However, seawater contains should be fully utilized to improve the scale inhibition effect. Gu et al. corrosive media such as chloride ions, sulfate ions and carbonate ions, [6] studied the formulation of scale inhibitors for oilfield water, and which can easily corrode equipment and cause potential danger [1,2]. found that when the formulation was 50 mg/L MA-AMPS and 8 mg/L In addition, the continuous evaporation and concentration of water will imidazoline, the scale inhibition rate could reach up to 93.42%, and the lead to the deterioration of circulating water quality, scaling on the corrosion inhibition rate of mild steel could reach up to 90.42%, with surface of equipment and pipelines, reducing the heat transfer capacity excellent corrosion inhibition performance. Meanwhile, with the de- of equipment, and even causing accidents such as boiler explosion. An velopment of green chemistry, an environment-friendly and efficient economical and practical way to control or inhibit the corrosion and composite inhibitor, which can overcome not only the corrosion pro- scaling in seawater utilization is the usage of corrosion and scale in- blem but also the scaling problem, has become the high priority of mild hibitors owing to their high efficiency, easy operation and low-price. steel protection. Considering that sodium citrate (SC) is nontoxic and The corrosion and scale inhibitors are believed to act by adsorbing their with excellent chelating ability to metal ions such as Ca2+and Fe2+, active functionalities on the steel surface and forming a film of physical and has strong abilities in biodegradation, dispersion and resistance to or chemical properties to isolate the steel from the aggressive en- redeposition [7,8], we anticipated that sodium citrate combined with vironment [3–5]. Various corrosion and scale inhibitors have been appropriate organic inhibitors can give a practical scaling-corrosion ⁎ Corresponding authors at: School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, PR China. E-mail addresses: [email protected] (H.-J. Li), [email protected] (Y.-C. Wu). https://doi.org/10.1016/j.desal.2020.114482 Received 1 March 2020; Received in revised form 17 April 2020; Accepted 20 April 2020 (OVHYLHU%9$OOULJKWVUHVHUYHG W. Zhang, et al. 'HVDOLQDWLRQ inhibitor platform for the application of steel in seawater. inhibitors at 30 °C for 72 h, and followed the methodological steps of As a kind of N-heterocyclic organic compounds, acridinium deri- the previous work [12]. Corrosion rate can be expressed by the fol- vatives are widely concerned because of their effective nitrogen atoms lowing relational Eq. (1): and conjugated π-bond structures, which can form coordination bonds WW− fi v = 12 with iron atoms to form a dense adsorption lm on the surface of steel st× (1) [5]. Moreover, acridinium-based materials have the characteristics of simple synthesis, low toxicity and unique anti-corrosion activity. Thus, where W1 and W2 (mg) are the weight loss of mild steel in the presence 2 the combination of acridinium derivatives with SC has a great appli- and absence of inhibitors, respectively, s (cm ) is the area of steel ffi η cation prospect in the scale and corrosion inhibition performance of samples, and t (h) is the soaking time [5]. The inhibition e ciency ( w) seawater utilization. was calculated by Eq. (2): In this study, acridine was synthesized for the first time via one-pot vvo − ηw = × 100% annulation of 2-aminobenzophenone and cyclohexanone in the pre- vo (2) sence of iodine under an atmosphere of oxygen, in which water was the only by-product. 10-Methylacridinium iodide (MAI), prepared by the where vo is the corrosion rate in the absence of inhibitor and v is the condensation of acridine and methyl iodide, was designed here as a corrosion rate in the presence of inhibitor. representative scaling-corrosion inhibitor for mild steel utilization, which combined with sodium citrate was used as a probe to estimate 2.3. Electrochemical measurements for corrosion inhibition the potential inhibition effect. The inhibition behavior of the mixture of MAI and SC was studied by weight loss method, potentiodynamic po- The electrochemical test system is identical to that described in our larization, electrochemical impedance spectroscopy (EIS). The stability previous reports [13,14]. Before each experiment, the working elec- fi of the inhibitor film was investigated by chronoamperometry (CA) at trode is rst contacted with the tested solution for 30 min to achieve its anodic and cathodic potentials. Scanning electron microscopy (SEM), stable open-circuit potential (OCP) at room temperature. Potentiody- scanning electrochemical microscopy (SECM) and X-ray photoelectron namic anodic and cathodic polarization curves were performed using a −1 − − spectroscopy (XPS) were used to measure the surface morphology of scan rate equal to 1 mV s from 900 mV up to 450 mV in relation adsorption film. The scale inhibition effect was determined by static to the stable OCP. Electrochemical impedance measurements were scale inhibition test. The scale inhibition mechanism of the inhibitor conducted over a frequency range from 100 kHz to 50 mHz at the stable was investigated by SEM and XRD. The scaling–corrosion mechanism open-circuit potential with an AC wave of 5 mV. CA measurements between the MAI–SC mixture and the mild steel surface was studied via were carried out by applying constant anodic and cathodic potentials quantum chemical calculation. for 1 h. 2. Experimental 2.4. Static tests for scale inhibition 2.1. Materials and solutions The scale inhibition performance was measured by CaCO3 deposi- tion method based on Chinese national standard method (GB/T 16632- Working electrodes were prepared from mild steel specimens with 2008) [3,15]. The tests were maintained for 10 h in a water bath at – the following composition: C (0.056%), Mn (0.18%), P (0.035%), Si 80 °C in the presence of a certain amount of the MAI SC mixture. The fi (0.26%), S (0.06%) and remainder Fe. The size of mild steel specimens solution was cooled to room temperature and ltered, and the content 2+ fi for weight loss, electrochemical, and surface analysis experiments have of residual Ca in the ltrate was titrated with EDTA. The scale in- ffi been detailed in our previous work [5]. Before each measurement, mild hibition e ciency can be calculated from Eq. (3): steel coupons were manually abraded with 400, 800 and 1000 mesh [Ca2++ ]− [Ca2 ] η = f o × 100% water grit papers, washed with double distilled water, degreased with s 2++2 [Ca ]i − [Ca ]o (3) ethanol and then dried in warm air. The experiments involved were 2+ 2+ fi carried out in a seawater solution without or with inhibitors. The ty- where [Ca ]f is the Ca concentration in the ltrate after heating 2+ 2+ fi pical composition of Weihai seawater was listed in Table S1 [Supple- with inhibitors, [Ca ]o is the Ca concentration in the ltrate after 2+ 2+ mentary Information]. heating without inhibitors, [Ca ]i is the Ca concentration in the Acridines were usually prepared from two aromatic substrates with starting solution. hazardous by-products and limited substrate scopes. To circumvent this problem, Wang et al. [9] have developed an elegant acridine synthesis 2.5. Surface analysis from 2-aminophenyl ketones and cyclohexanones using hazardous tert- butyl hydroperoxide as the oxidant.