Synthesis of polyaspartic acid-glycidyl adduct and evaluation of its scale inhibition performance and corrosion inhibition capacity for Q235 steel applications

In this work, the development of the eco-friendly comprehensive scale and corrosion inhibitor based on green polyaspartic acid (PASP) was presented. In this view, PASPG was prepared by a ring-opening graft modification reaction of polysuccinimide (PSI) with glycidyl. In addition, the molecular structure and the thermal stability of PASPG were characterized by using three different methods (FTIR, ¹H NMR, and TGA). PASPG’s scale inhibition efficiency and corrosion inhibition efficiency were also evaluated, respectively. More concretely, the scale inhibition efficiency of PASPG achieved 94.6 % and 95.1 % for CaCO₃ and CaSO₄, respectively. With the aid of the FTIR and SEM measurement techniques, it was found that PASPG could induce the irregular growth of the CaCO₃ and CaSO₄ morphology and destroy the formation of crystals. On the other hand, the higher corrosion efficiency of 85.17 % was achieved by PASPG in comparison with PASP (72.53 %). PASPG is a mixed inhibitor and the adsorption of PASPG on the Q235 steel surface followed the Langmuir mono-layer adsorption isotherm. The formation of a protective film on the surface of carbon steel was proved by PASPG’s adsorption, which increased the resistance to be eroded. Thus, the surface of carbon steel can be effectively protected. The present work provides a simple and effective pathway for the synthesis of high-efficiency green scale and corrosion inhibitor, by introducing a functional group into the PASP chains. The implementation of such type of chemical modification method may also be an effective strategy for improving the efficiency of other polymers green scale and corrosion inhibitors.     

Preparation of fluorescent polyaspartic acid and evaluation of its scale inhibition for CaCO3 and CaSO4

Polysuccinimide was synthesized from maleic anhydride and urea. A polyaspartic acid derivative (PASP‐Try‐SEA) was synthesized from the polysuccinimide with 2 ‐aminoethanesulfonic acid and tryptophan. The products were characterized by UV, FTIR,¹H NMR, TGA and PL, respectively. The results showed that the fluorescent chromophore‐indolyl groups were successfully incorporated into PASP. The relationship between the fluorescence intensity and the concentration of fluorescent polyaspartic acid (FPASP) is linear with the excitation wavelength of 366 nm and 422 nm. FPASP also showed excellent scale inhibition properties with a scale inhibition rate of 78% achieved for CaCO₃ with a dosage of 9 mg/L and a significantly enhanced scale inhibition effect for CaSO₄, achieving an inhibition rate of 98%, which were determined using the static scale inhibition method. When FPASP was added to the solution, CaCO₃ and CaSO₄ deposits showed flower patterns with floppy accumulation by scanning electron microscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

Molecular Dynamics Simulation on Scale Inhibition Mechanism of Polyepoxysuccinic Acid to Calcium Sulphate

Molecular dynamics simulation has been performed to simulate the interaction between PESA and the (001) face of anhydrite crystal CaSO₄ at different temperatures with the presence of various number of H₂O molecules. The results show that PESA can effectively prevent the growth of CaSO₄ scale at 323-343 K. At the same temperature, the binding energy between PESA and the (001) face of CaSO₄ for systems with various number of H₂O has the order of E_bind(0H₂O)>E_bind(200-400H₂O)>E_bind(100H₂O). For the same system at different temperatures the binding energies are close and are mainly contributed from the Coulomb interaction, including ionic bonds. The bonds are formed between the calcium atoms of anhydrite scale crystal and the oxygen atoms of the carboxyl group of PESA. Hydrogen bonds are formed between the O atoms of the carboxyl group of PESA and the H atoms of H2O. van der Waals interaction is conducive to the stability of the system of PESA, H₂O, and CaSO₄. The radial distribution functions of O(carbonyl of PESA)-H(H₂O),O(CaSO₄)-H(H₂O), and O(CaSO₄)-H(PESA) imply that solvents have effects on the anti-scale performance of PESA to CaSO₄.     

Experimental study on scale inhibition performance of a green scale inhibitor polyaspartic acid

Static and dynamic experiments were carried out to validate scale inhibition performance of a green scale inhibitor-polyaspartic acid (PASP). From the static experiment, it was shown that below 60℃, polyaspartic acid is very effective in scale inhibition, with the scale inhibition ratio exceeding 90% with only 3 mg/L PASP for the 600 mg/L hardness solution. For a higher hardness solution of 800 mg/L, the scale inhibition ratio can also reach 90% with 6 and 12 mg/L PASP at 30 and 60℃respectively. The SEM photographs of CaCO3 crystals indicate that the crystal structure transforms from a compact stick-shape to a loose shape so that the scale can be washed away easily instead of being deposited on the heat transfer surface. The dynamic experimental results show that almost no scales formed on the heat trans- fer surface and the fouling thermal resistance decreases extraordinarily if PASP is added in the solution.     

Scale Inhibition of Green Inhibitor Polyepoxysuccinic Sodium

Polyepoxysuccinic acid (PESA) is the green water treatment agents recognized all over the world[1-3]. It is found that when PESA is used alone, it had good scale inhibition. PESA should be included in the category of green scale inhibitor.PESA is synthesized with maleicanhydride in the presence of catalysts. The effect on scale-in-hibiting property of the product from amount and feed times of catalyst, the reaction temperature, the reaction time were investigated. The optimum reaction conditions are as follows:n(maleic anhydride):n(Ca(OH)2):n(NaOH)=1:0.05-0.2:0.5, reaction temperature 95C, reaction time 4h.In all the references about PESA, PESA is researched as a kind of highly effective scale inhibitor or chelate. In this paper, the performance of scale inhibition of PESA is evaluated by scale static inhibitor.The results are shown in Figture1.It is evident from our experimental data (Figture1) that when inhibition for CaCO3.With the increase of PESA dosage, scale inhibition increases. When dosage is more than 6mg/L, inhibition efficiency is over 50%. The formulas give scale inhibition efficiency more than 95% at 12mg/L of total dosage.     

Vacuum balance studies of milled material and mechanochemical reactions

The types of change in surface properties and porosity of milled materials having widely different hardness and crystal structure are reviewed. For more intensive milling, the use of vacuum balance techniques in conjunction with X-ray diffraction, optical- and electron-microscopy enables changes in microstructure and phase composition to be determined during mechanochemical reactions.Metallic or non-metallic harder materials (Mohs scale 8–9), such as transition metal nitrides or silicon nitride and boron carbide, increase their surface on milling largely due to brittle fracture, so that the surface area tends towards an upper limiting value with comparatively little development of porosity.Softer materials (Mohs scale 1–2), such as gypsum, china clay(Kaolinite) and hydrated lime and magnesia undergo plastic deformation and strain hardening on longer milling, so that the surface area passes through a maximum before decreasing to an equilibrium value. This is applicable also to materials of intermediate hardness (Mohs scale 3–5), such as calcite, magnesite and dolomite, provided that the milling is sufficiently intensive; the flow and welding processes during the plastic deformation leave the grains non-porous to nitrogen gas, but adsorption of water vapour causes development of porosity, a phenomenon also observed with lunar fines (mainly silicate minerals) which are of somewhat greater hardness but contain amorphous surface layers (cf. Beilby layer) and nuclear particle damage tracks having tubular pores with narrow constrictions forming micropores.More intensive milling can result in crystal transformation and mechanochemical reactions. Thus gypsum is converted to anhydrite, viz., CaSO₄.2H₂O → CaSO₄.2H₂O → γ—CaSO₄ → β—CaSO₄. Calcite, CaCO₃, is converted to aragonite, while calcitic CaCO₃ and magnesite, MgCO₃, form dolomite CaCO₃.MgCO₃.     

Morphology and Kinetics of Growth of CaCO<Subscript>3</Subscript> Precipitates Formed in Saline Water at 30°C

The crystallization kinetics and morphology of CaCO₃ crystals precipitated from the high salinity oilfield water were studied. The crystallization kinetics measurements show that nucleation and nuclei growth obey the first order reaction kinetics. The induction period of precipitation is extended in the high salinity solutions. Morphological studies show that impurity ions remain mostly in the solution phase instead of filling the CaCO₃ crystal lattice. The morphology of CaCO₃ precipitates can be changed from a smooth surface (calcite) to rough spheres (vaterite), and spindle rod bundles, or spherical, ellipsoid, flowers, plates and other shapes (aragonite).     

Corrosion Inhibition of a Green Scale Inhibitor Polyepoxysuccinic Acid

The corrosion inhibition of a green scale inhibitor, polyepoxysuccinic acid (PESA) was studied based on dynamic tests. It is found that when PESA is used alone, it had good corrosion inhibition. So, PESA should be included in the category of corrosion inhibitors. It is not only a kind of green scale inhibitor, but also a green corrosion inhibitor. The synergistic effect betweenPESA and Zn2 or sodium gluconate is poor. However, the synergistic effect among PESA, Zn2 and sodium gluconate is excellent, and the corrosion inhibition efficiency for carbon steel is higher than 99%. Further study of corrosion inhibition mechanism reveals that corrosion inhibition of PESA is not affected by carboxyl group, but by the oxygen atom inserted. The existence of oxygen atom in PESA molecular structure makes it easy to form stable chelate with pentacyclic     

Peanut-shaped aggregation of CaCO<Subscript>3</Subscript> crystallites in the presence of an amphiphilic derivative of carboxymethylchitosan

An amphiphilic derivative of carboxymethylchitosan (CMCS), (2-hydroxyl-3-butoxyl)propyl-CMCS (HBP-CMCS), was used as an organic additive in the precipitation process of calcium carbonate (CaCO₃). HBP-CMCS molecules can interact with calcium ions, the functional groups of which act as active sites for the nucleation and crystallization of CaCO₃. Simultaneously, HBP-CMCS molecule also functionalizes as a colloidal stabilizer to prohibit the sedimentation of the grown CaCO₃ crystals, depending upon the molar ratio of the initial Ca²⁺ ions to the repeat units of HBP-CMCS molecules. The combination investigations of scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy on the precipitated CaCO₃ crystals proved that concentrations of HBP-CMCS and Ca²⁺ exert great influence on the crystallization habit of CaCO₃, such as the nucleation, growth, morphology, crystal form, etc. The formation of the peanut-shaped CaCO₃ particles suggests the template effect of HBP-CMCS molecules on the aggregation behavior of CaCO₃ nanocrystals.     

Alginate hydrogel-mediated crystallization of calcium carbonate

We documented a specific method for combining calcium ions and alginate molecules slowly and continuously in the mineralization system for the purpose of understanding the mediating function of alginate on the crystallization of calcium carbonate. The alginate was involved in the nucleation and the growth process of CaCO₃. The crystal size, morphology and roughness of crystal surface were significantly influenced by the type of the alginate, which could be accounted for by the length of the G blocks in alginate. A combination of Fourier transform infrared spectroscopy and thermogravimetric analysis showed that there were the chemical interactions between the alginate and the mineral phase. This strategic approach revealed the biologically controlled CaCO₃ mineralization within calcium alginate hydrogels via the selective nucleation and the confined crystallization of CaCO₃. The results presented here could contribute to the understanding of the mineralization process in hydrogel systems.     

Formation of calcium sulfate whiskers from CaCO3-bearing desulfurization gypsum

Calcium sulfate whiskers can be used as the reinforcing agents in many composites, such as polymers, ceramics, cements, and papers, etc. This paper investigated the feasibility of preparing calcium sulfate whiskers using desulfurization gypsum as the raw material. The desulfurization gypsum composed mainly of CaSO₄·2H₂O (93.45 wt%) and CaCO₃ (1.76 wt%) were treated with dilute H₂SO₄ at room temperature to convert CaCO₃ to CaSO₄; the latter was then treated at 110?C150 °C to form CaSO₄·0.5H₂O whiskers. The removal of the CaCO₃ impurity from the desulfurization gypsum favored the formation of CaSO₄·0.5H₂O whiskers with high aspect ratios.     

St / AA共聚物的组成对碳酸钙结晶及形貌影响的研究

在聚苯乙烯-丙烯酸两亲共聚物(简称PAS)溶液中制备CaCO₃，用XRD、FTIR和SEM等研究随着PAS的亲水AA和亲油St单元组成的变化所引起的聚合物分子链段、溶解性质和胶束空间构象等的改变对CaCO₃晶型和形貌的影响。结果显示：随着亲水性AA单元组成的提高，可以由AA链段的晶面匹配成核调控碳酸钙为方解石纳米晶，并因PAS在水溶液中溶解性不同，形成了多种碳酸钙形貌的聚集体；当St和AA的物质的量比为3∶1时，合成出类珍珠岩层碳酸钙结构。根据PAS的结构性质和在水溶液中的溶解行为初步探讨了类珍珠岩层碳酸钙的形成机理，认为是PAS基质模板和羧酸根对钙的键合作用形成这一特殊形貌碳酸钙。     

The effect of polyacrylic acid and reaction conditions on nanocluster formation of precipitated calcium carbonate on microcellulose

The precipitation of micro- and nanoparticles of calcium carbonate onto lignocellulosic microfibers was investigated at different microfiber concentrations with and without polyacrylic acid (PAA), i.e. a polymer commonly used to form polymer-induced liquid precursors of CaCO₃. Concentrations of PAA, Ca(OH)₂, CO₂ and microfiber were varied in order to study the impact of reaction conditions on PCC formation in a batch reactor operated at ambient temperature. High resolution scanning electron micrographs of the samples show that both microfiber concentration and PAA dosage affected the nucleation and crystal growth of PCC filler on cellulosic fiber. Interestingly, at higher microfiber concentrations, larger amount of nano-sized spherical crystals were formed on the microfibers. A higher dosage of PAA, on the other hand, resulted in less nucleation on the microfiber, suggesting a preferential bulk nucleation mechanism. A higher concentration of PAA during the precipitation also led to the formation and stabilization of amorphous CaCO₃, which was supported by SEM images and XRD analysis (lack of characteristic crystal structure).     

Molecular dynamics simulation on the interaction between polymer inhibitors and anhydrite surface

Investigation on the microscopic interaction between polymer inhibitors and calcium sulfate will be helpful for understanding its scale inhibition mechanism and can provide a theoretical guidance to developing new scale inhibitors. In this work, molecular dynamics simulations with COMPASS force field have been performed to simulate the interaction between hydrolyzed polymaleic anhydride (HPMA), polyaspartic acid (PASP), polyepoxysuccinic acid (PESA), polyacrylic acid (PAA) and the (001) and (020) surfaces of anhydrite (AD) crystal with and without water. The results show that the sequence of binding energies between four polymer inhibitors and AD (001) and (020) with water is PESA > PASP > HPMA > PAA. The binding energy of the same polymer inhibitor on AD (001) is smaller than that on AD (020). Water molecules weaken the deformations of HPMA and PAA but aggravate those of PASP and PESA. Natural bond orbital (NBO) charges of the repeat units of polymer inhibitors were calculated by B3LYP/6‐31G* method. The Coulomb interaction is formed between the O atoms of polymer inhibitors and the Ca atoms of AD crystal. The system of polymer–AD is mainly contributed from the non‐bonding interaction. Polymer inhibitors do not interact directly with AD crystal, but indirectly through the interactions between inhibitor–H₂O and H₂O–AD, i.e. water molecules participate in scale inhibition of polymer inhibitors to AD crystal. Water molecules cannot be ignored when the interaction models are constructed, i.e. solvent effect cannot be ignored. Copyright © 2015 John Wiley & Sons, Ltd.     

Na5P3O10-Ca(OH)2-CO2-H2O体系纳米CaCO3的成核与生长

通过化学分析、SEM显微分析技术,结合Rosin-Ramiler概率统计理论,从介观层次研究Na5P3O10-Ca(OH)2-CO2-H2O体系纳米CaCO3的合成反应及其成核和生长过程。结果表明,Na5P3O10对Ca(OH)2的碳化反应具有抑制作用。随着[Na5P3O10]的增加,体系中CaCO3的成核速率B^0逐渐增大。在[Na5P3O10]＝0ppm时,CaCO3结晶的生长由长程扩散和凝聚生长控制;[Na5P3O10]=380.4,760.9ppm时,前期受短程扩散和界面反应控制、后期受长程扩散控制。Na5P3O10的存在,抑制了纳米CaCO3的晶体生长。     

Investigation of Calcium Carbonate Scaling Inhibition and Scale Morphology by AFM

The calcium carbonate scale inhibition by two inhibitors, polyacrylic acid (PAA) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), has been studied in two heat transfer systems: recirculating cooling water and pool boiling systems. It is found that PBTCA has a better inhibition effect than PAA under identical conditions. The inhibition effect increases with increasing fluid velocity for the cooling water system, whereas in the presence of inhibitors, the fluid velocity has less effect on the scaling behavior. When the initial surface temperature increases, the inhibition efficiency decreases. In the presence of inhibitors, the scaling behavior is insensitive to the change of surface temperature. The relationship between the inhibition effect and the fractal dimension has also been investigated. The results show that the fractal dimension is higher in the presence of inhibitors. The better the inhibition effect, the higher the fractal dimension. XRD and FTIR analyses demonstrate that for the CaCO₃ formed in the pool boiling system, the content of vaterite increases with the increase of inhibition effects. The metastable crystal forms of vaterite and aragonite are stabilized kinetically in the presence of inhibitors. The step morphology has been observed by atomic force microscopy. It is shown that the step space on the CaCO₃ surface increases in the presence of inhibitors. Moreover, with the increase in inhibition effect, both the step space and the fractal dimension increase. Step bunching is also found and discussed in this paper.     

Crystal growth of CaCO3 induced by monomethylitaconate grafted polymethylsiloxane

We report the preparation of a new monomethylitaconate grafted polymethylsiloxane (CO₂H-PMS) copolymer and its effect as template for crystal growth of CaCO₃. The in vitro crystallization of CaCO₃ was carried out using the gas diffusion method at different pH values at room temperature for 24 h. The CO₂H-PMS was prepared using polydimethylsiloxane-co-methylhydrogensiloxane (PDMS-co-PHMS), obtained through cationic ring opening polymerization, from cyclic monomers and monomethyltaconate (MMI) via hydrosilylation reactions with platinum complex as catalyst. FTIR results are in an agreement with the proposed template structure and confirmed that the hydrosilylation was complete. Experimental results from pH values and SEM analysis showed that the carboxylate groups of CO₂H-PMS alter the nucleation, growth and morphology of CaCO₃ crystals. SEM revealed single-truncated (ca. 5 μm) modified at pH 7-9, aggregated-modified (ca. 20 μm) at pH 10-11, and donut-shaped crystals at pH 12. These morphologies reflect the electrostatic interaction of carboxylic moieties with Ca²⁺ modulated by CO₂H-PMS adsorbed onto the CaCO₃ particles. EDS confirmed the presence of Si atoms on the crystals surface. XRD analysis showed the existence of only two polymorphs: calcite and vaterite revealing a selective control of CaCO₃ polymorphisms. In summary, the use of grafted polymethylsiloxane template offer a good alternative for polymer controlled crystallization and a convenient approach for understanding the biomineralization process useful for the design of novel materials.     

Effects of Hydroxypropylmethylcellulose macromolecules used as organic template on the crystallization of CaCO<Subscript>3</Subscript>

Hydroxypropylmethylcellulose (HPMC) was used as an organic template to synthesize calcium carbonate. Crystals were synthesized in HPMC solution and HPMC hydrogel, respectively. For the mineralization system of HPMC solution, the effects of adding HPMC and rotating the reaction system on the crystal polymorph and morphology of CaCO₃ were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results showed that the presence of HPMC induced the formation of aragonite. And its content became higher when the concentration of solution increased or when rotating the system with the presence of HPMC. Moreover, it can be seen from SEM that bundle-like CaCO₃ appeared and became more with the increase of concentration. The structure and shape of the crystal had close relationship with the condition of mineralization. On the other hand, for the first time, CaCO₃ was synthesized in HPMC gel, SEM results indicated that a special structure, a long bar with some slight slots at intervals on the surface, of the crystals which may be caused by the network structure of the gel was found. Thermogravimetry (TG) results showed that CaCO₃ crystal products contained some HPMC. Further research on how the gel network modulates the growth of crystals is left to be done in the future.     

Die bestimmung kinetischer parameter endothermer zersetzungsreaktionen unter nicht-isothermen bedingungen

By using the kinetic parameters calculated from non-isothermal measurements according to Freeman and Carroll a computer programm is given, which permits the determination of the more probable reaction mechanism by use of 17 different kinetic equations. The computer programm includes the kinetic equation for chemical reaction, nucleation, phase boundary reaction and diffusion and can easily be extended to other equations. The evaluation of the experimental values by a distinct kinetic equation is quantitatively characterized by means of the correlation coefficient.The kinetic parameters are calculated on the basis of a regression analysis. By dividing the thermogravimetric curve in different reaction intervals a differential calculation is possible.Decomposition of CaCO₃, MgCO₃ and CaSO₄·2H₂O is discussed from the results of the computer calculation. It is seen that the kinetic parameters and the reaction mechanism are not constant during the reaction. Further experiments for a physical interpretation are being carried out.     

聚电解质膜PDAC/PSS诱导CaCO3结晶的研究

以模拟软体动物珍珠层的周期性基质控制形成过程制备仿生层状复合材料. 将聚苯乙烯磺酸钠(PSS)与聚二烯二甲基氯化铵(PDAC)用逐层浸渍的方法使其组装成多层膜, 用于诱导过饱和溶液中CaCO₃的结晶, 详细研究了膜紫外吸收随组装层数增加的线性变化. 扫描电镜和X射线衍射表征了晶体的形貌和结构. (PDAC/PSS)₁₅PDAC膜诱导获得的CaCO₃晶体为六面体结构, 晶体尺寸为30～40 μm; (PDAC/PSS)₁₅膜诱导CaCO₃结晶, 可以在膜表面获得形貌与珍珠层非常相似的CaCO₃晶体, 结晶10 h获得的晶片结构呈规则的六边形, 片尺寸约为10～20 μm. X射线衍射结果表明两种晶体的晶格结构与天然珍珠层差异明显, 说明静电作用为晶体形貌的主控因素之一, 但不是晶格结构的决定因素. 复合材料断面电镜照片表明其为层状结构.