Formation and Inhibition of Calcium Carbonate Crystals under Cathodic Polarization Conditions

Green and sustainable strategies to control scaling in industrial plants: investigation of the efficacy of Rosmarinus officinalis L. Extract against CaCO3 scale using experimental and theoretical approaches

In recent years, plant extracts have attracted increased interest as green alternatives to conventional anti-scaling. This is because they contain a wide range of bioactive compounds with high performance against inorganic scale. Additionally, they are biodegradable and pose minimal risks to human health and ecosystems. The present study aimed to assess the protection offered by the Rosmarinus officinalis L. leaf extract for industrial plant surfaces against the CaCO3 scale. Before assessing the anti-scaling performance of the Rosmarinus extract, phytochemical characterisation was performed by quantitative assays and HPLC-DAD analysis. Subsequently, the inhibition potential of the extract was studied using the conductivity and LCEE tests at 25°C and TH = 40°f. In addition, SEM and XRD analysis were used to assess the effect of the extract on scale morphology and crystalline phases. Finally, DFT calculations and Monte Carlo simulation were carried out to enhance knowledge of the interaction between inhibitor molecules and CaCO3(104) and (110) surfaces and optimise [extract molecule - Ca]2+ complexes. Phytochemical analysis revealed the presence of several phenolic compounds (rosmarinic acid, vanillic acid, cinnamic acid, rutin, kaempferol, trans chalcone and quercetin). Further LCEE studies demonstrated the promising anti-scaling activity of the extract at an effective concentration of 54 mg/L. SEM micrographs and XRD diffractograms revealed a significant change in the morphology and phases of precipitated CaCO3 scales upon the addition of the inhibitor. In addition, the computational approach strongly supported the experimental results. These results underlined the Rosmarinus extract's potential as a valuable green and sustainable scaling inhibitor source.

Review on descaling and anti-scaling technology of heat exchanger in high-salt wastewater thermal desalination

Thermal desalination evaporation of high-salt wastewater has been widely used in industry because of the proposed concept of 'zero liquid discharge'. However, due to the high content of Ca2+ and Mg2+ in high-salt wastewater, the heat exchanger, as the main treatment equipment, suffers from serious scaling problems. This review presents descaling and scale inhibition technologies of high-salt wastewater. The advantages and disadvantages of various technologies are summarized and analyzed to provide theoretical support for the research of descaling and anti-scaling of heat exchangers with high-salt wastewater. In future industrial development, the synergistic application of electromagnetic water treatment technology and scale inhibitors can significantly improve the anti-scaling effect, which can reach over 95% stably. Furthermore, the addition of a physical field can also expand the application range of scale inhibitors.

Review of Phosphorus-Based Polymers for Mineral Scale and Corrosion Control in Oilfield

Production chemistry is an important field in the petroleum industry to study the physicochemical changes in the production system and associated impact on production fluid flow from reservoir to topsides facilities. Mineral scale deposition and metal corrosion are among the top three water-related production chemistry threats in the petroleum industry, particularly for offshore deepwater and shale operations. Mineral scale deposition is mainly driven by local supersaturation due to operational condition change and/or mixing of incompatible waters. Corrosion, in contrast, is an electrochemical oxidation-reduction process with local cathodic and anodic reactions taking place on metal surfaces. Both mineral scaling and metal corrosion can lead to severe operational risk and financial loss. The most common engineering solution for oilfield scale and corrosion control is to deploy chemical inhibitors, including scale inhibitors and corrosion inhibitors. In the past few decades, various chemical inhibitors have been prepared and applied for scaling and corrosion control. Phosphorus-based polymers are an important class of chemical inhibitors commonly adopted in oilfield operations. Due to the versatile molecular structures of these chemicals, phosphorus-based polymeric inhibitors have the advantage of a higher calcium tolerance, a higher thermal stability, and a wider pH tolerance range compared with other types of inhibitors. However, there are limited review articles to cover these polymeric chemicals for oilfield scale and corrosion control. To address this gap, this review article systematically reviews the synthesis, laboratory testing, and field applications of various phosphorus-based polymeric inhibitors in the oil and gas industry. Future research directions in terms of optimizing inhibitor design are also discussed. The objective is to keep the readers abreast of the latest development in the synthesis and application of these materials and to bridge chemistry knowledge with oilfield scale and corrosion control practice.

A Case Study of Calcium Carbonate Crystallization during Reverse Osmosis Water Desalination in Presence of Novel Fluorescent-Tagged Antiscalants

Calcium carbonate scaling in reverse osmosis (RO) desalination process is studied in the presence of two novel fluorescent-tagged scale inhibitors 1,8-naphthalimide-tagged polyacrylate (PAA-F1) and 1-hydroxy-7-(6-methoxy-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)heptane-1,1-diyl-bis(phosphonic acid) (HEDP-F) by fluorescent microscopy (FM) and scanning electron microscopy (SEM). Both antiscalants diminished the mean size of calcite crystals relative to the blank experiment. The behavior and localization of HEDP-F and PAA-F1 during calcite scale formation on membrane surface was found to be significantly different from the distribution in similar RO experiments with gypsum, reported earlier. In the former case, both antiscalants are concentrated exactly on the surface of calcium carbonate crystals, while in the latter one they form their own phases (Ca-HEDP-F and Ca-PAA-F1) and are not detected on gypsum scale. The difference is interpreted in terms of interplay between background calcium concentration and sparingly soluble calcium salts’ solubility. HEDP-F reveals slightly higher efficiency than PAA-F1 against calcite scale formation, while PAA-F exhibits a higher ability to change calcite morphology. It is demonstrated that there is a lack of correlation between antiscaling efficacy and ability of antiscalant to change calcium carbonate morphology in a particular case study. An application of fluorescent-tagged antiscalants in RO experiments provides a unique possibility to track the scale inhibitor molecules’ localization during calcite scale formation. Fluorescent-tagged antiscalants are presumed to become a very powerful tool in membrane scaling inhibition studies.

Hydrophobic Composites Designed by a Nonwoven Cellulose-Based Material and Polymer/CaCO3 Patterns with Biomedical Applications

Herein, we report a simple method to obtain hydrophobic surfaces by surface modification with calcium carbonate via diffusion-controlled crystallization using a cheap, versatile, and super-hydrophilic cellulose-based nonwoven material (NWM) as the substrate. To control the CaCO₃ crystal growth, the ammonium carbonate diffusion method was applied in the presence of polyanions [poly(acid acrylic), poly(2-acrylamido-2-methylpropanesulfonic acid), and a copolymer which contains 55 mol % 2-acrylamido-2-methylpropanesulfonic acid and 45 mol % acrylic acid] or nonstoichiometric polyelectrolyte complexes with polycations [poly(allylamine hydrochloride) and chitosan] on a pristine NWM and on polycation-treated surfaces. The surface morphology obtained by calcite growth under surface or environmental functional groups' influence and the hydrophilic/hydrophobic character of the composite materials were followed and compared to that of the starting material. The obtained composite materials become hydrophobic, having a contact angle in the range of 110-135°. The capacity of tetracycline sorption and release by selected modified surfaces were followed and compared to the untreated NWM. Also, the biological properties were evaluated in terms of biocompatibility, antibacterial activity, and antifouling capability.

Synthesis and Visualization of a Novel Fluorescent-Tagged Polymeric Antiscalant during Gypsum Crystallization in Combination with Bisphosphonate Fluorophore

An attempt to reveal the mechanisms of scale inhibition with the use of two different fluorescent-tagged antiscalants at once is undertaken. To reach the goal, a novel 1,8-naphthalimide-tagged polyacrylate (PAA-F2) is synthesized and tested separately and jointly with 1,8-naphthalimide-tagged bisphosphonate (HEDP-F) as a gypsum scale inhibitor within the frames of NACE Standard TM0374-2007. Here, it is found that at a dosage of 10 mg·dm−3 it provides a much higher inhibition efficiency (96%) than HEDP-F (32%). A PAA-F2 and HEDP-F blend (1:1 mass) has an intermediate efficacy (66%) and exhibits no synergism relative to its individual components. The visualization of PAA-F2 revealed a paradoxical effect: an antiscalant causes modification of the CaSO4·2H2O crystals habit, but does not interact with them, forming particles of its own solid complex [Ca-PAA-F2]. This paradox is interpreted in terms of the “nano/microdust” concept, prioritizing the bulk heterogeneous nucleation step, while an ability of the scale inhibitor to block the nucleus growth at the next steps is proven to be of secondary importance. At the same time, HEDP-F does not change the gypsum crystals morphology, although this antiscalant is completely located on the surface of the scale phase. The PAA-F2 and HEDP-F blend revealed an accumulation of both antiscalants in their own [Ca-PAA-F2/Ca-HEDP-F] phase with some traces of HEDP-F and PAA-F2 on the CaSO4·2H2O crystals surface. Thus, the visualization of two different antiscalants separately and jointly applied to gypsum deposition demonstrates differences in phosphonic and polymeric inhibitors location, and a lack of causal relationship between antiscalant efficiency and scale particle habit modification. Finally, it is shown that the confocal microscopy of several fluorescent antiscalant blends is capable of providing unique information on their interrelationships during scale deposition.