The formation of calcium carbonate in water has some important implications in geoscience researches, ocean chemistry studies, CO2 emission issues and biology. In industry, the scaling phenomenon may ...cause technical problems such as reduction of heat transfer efficiency in cooling systems and obstruction of pipes.
The use of chemicals which act as antiscalant is a common approach in the control of scale deposition. However, inorganic nitrogen and phosphorous compounds are involved in eutrophication process. Therefore, it is of prime importance to find alternative solutions, i.e. green inhibitors of scale formation. This last decade, several new scale inhibitors, that are more ecological compared with conventional inhibitors, have been reported in the literature. Plant extracts have been also recently used as new green antiscalants. Indeed, as they can be easily extracted and are environmentally friendly, they represent an interesting alternative source of "natural" organic molecules.
In this review, a focus of some green antiscalants derived from petrochemicals has been reported. Then the efforts done those last years to obtain green inhibitors, either by using “natural” organic molecules or extracted from plants were summarized. Such green inhibitors might be used in various technical areas, i.e. energy, water, food and beverages industries.
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•A lot of efforts have been done to obtain green inhibitors.•They could be obtained from plant extraction or by using natural organic molecules.•Such green inhibitors might be used in varied technical areas, i.e. energy, water, food and beverages industries.
The green complex S = 1 (TPEN)FeO2+ TPEN = N,N,N‘,N‘-tetrakis(2-pyridylmethyl)ethane-1,2-diamine has been obtained by treating the (TPEN)Fe2+ precursor with meta-chloroperoxybenzoic acid (m-CPBA). ...This high-valent complex belongs to the emerging family of synthetic models of FeIVO intermediates invoked during the catalytic cycle of biological systems. This complex exhibits spectroscopic characteristics that are similar to those of other models reported recently with a similar amine/pyridine environment. Thanks to its relative stability, vibrational data in solution have been obtained by Fourier transform infrared. A comparison of the FeO and Fe18O wavenumbers reveals that the Fe−oxo vibration is not a pure one. The ability of the green complex to oxidize small organic molecules has been studied. Mixtures of oxygenated products derived from two- or four-electron oxidations are obtained. The reactivity of this FeO2+ complex is then not straightforward, and different mechanisms may be involved.
In this work, the scaling protection performance of Zn2+ and Cu2+, added to a phosphosilicate hybrid sol-gel coating and applied on both carbon and stainless steel surface, was evaluated for the ...first time in a solution containing initially 200 mg.L−1 of Ca2+ (corresponding to a water hardness of 50 °F) at 30 °C. Inhibition efficiency was estimated using chronoamperometry (CA) and quartz crystal microbalance (QCM). Results showed that these smart coatings were efficient to protect steel surface against scaling phenomenon. The coatings containing the Cu2+ inhibitor was the most effective of the systems tested. Moreover, CA and QCM measurements showed that the formation of calcium carbonate deposition on carbon steel decreased when the amount of zinc and copper ions added to the sol-gel film increased. Scanning electronic microscopy and X-ray diffraction results indicated that both cations included in the sol-gel film affected calcium carbonate nucleation by changing the morphology of CaCO3 crystals.
•Scaling tests are applicable to deposited sol-gel coating on steel.•Antiscalant effect of cations doped smart sol-gel phosphosilicate coating.•Effect of doping cations on calcium carbonate phases.
Scale deposition is a common issue in industrial plants, which creates technical problems, i.e. reduction of heat transfer, decrease of flow rate due to an obstruction of pipes. Therefore, the ...development of some appropriate methods based on well suitable in situ sensors to evaluate and predict the scaling propensity of water is a major concern in current research. This would be a good strategy for the optimization of anti-scaling treatments.
In this study, scaling tests were carried out using a sensitive sensor, which has been developed using a quartz crystal microbalance with a pre-calcified electrode surface (SQCM). This technique allowed studying the influence of the supersaturation on the scaling rate. The set-up was tested with different water samples which were brought to a given supersaturation coefficient by degassing the dissolved CO2. The prediction of the scaling propensity of water was then possible through the relationship between the scaling rate on a pre-calcified surface and the supersaturation coefficient. In addition, the kinetics of CaCO3 deposit on the pre-calcified SQCM surface was found to be slower for natural water than for synthetic water (same calcium concentration). Furthermore, the activation energy for scale deposit, in synthetic water, was found to be 22 kJ.mol−1, which may be related to the diffusion of ions and/or CaCO3 nuclei in solution.
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•A pre-calcified sensitive surface was used for scaling detection.•Scaling quartz crystal microbalance measured the scaling propensity of water.•An activation energy was found to be equal at 22 kJ.mol−1 for synthetic water.•The kinetics of CaCO3 deposit is slower for natural water than for synthetic water.
The Mn4 complex which is involved in water oxidation in photosystem II (PSII) is known to exhibit two types of EPR signals in the S2 state, one of the five redox states of the enzyme cycle: either a ...multiline signal (S = 1/2) or a signal at g = 4.1 (S = 3/2 or S = 5/2). The S = 1/2 state can be converted to that responsible for the g = 4.1 signal upon the absorption of near-infrared (IR) light Boussac, A., Girerd, J.−J., and Rutherford, A. W. (1996) Biochemistry 35, 6984−6989. It is shown here that a third state gives rise to signals at g = 10 and 6. This state is formed by IR illumination of the S = 1/2 state at 65 K, a temperature where IR illumination leads to the loss of the S = 1/2 signal but to no formation of the g = 4.1 state. On the basis of the corresponding decrease of the S = 1/2 state, the new state can be trapped in ∼40% of the PSII centers. Warming of the sample above 65 K, in the dark, leads to the loss of the g = 10 and 6 resonances with the corresponding appearance of the g = 4.1 signal. It is suggested that the IR-induced conversion of the S = 1/2 state into the g = 4.1 state at 150 K involves the transient formation of the new state. The new state is attributed to a S = 5/2 state of the Mn4 complex (although a S value > 5/2 is also a possibility). Spectral simulations indicate an E/D ratio of −0.05 with |D| ≤ 1 cm-1. The resonances at g = 10 and 6 correspond to the gz of the ±5/2 and ±3/2 transition, respectively. The temperature-dependent conversion of this S = 5/2 state into the g = 4.1 state is proposed to be due to relaxation of the ligand environment around the Mn4 cluster that leads to a change in the zero field splitting parameters, assuming an S = 5/2 value for the g = 4.1 state. The new form of the S2 state reported here may explain some earlier data where the S2 state was present and yet not detectable as either a S = 1/2 or a g = 4.1 EPR signal.
Superoxide reductase (SOR) is an Fe protein that catalyzes the reduction of superoxide to give H2O2. Recently, the mutation of the Glu47 residue into alanine (E47A) in the active site of SOR from ...Desulfoarculus baarsii has allowed the stabilization of an iron−peroxo species when quickly reacted with H2O2 Mathé et al. (2002) J. Am. Chem. Soc. 124, 4966−4967. To further investigate this non-heme peroxo−iron species, we have carried out a Mössbauer study of the 57Fe-enriched E47A SOR from D. baarsii reacted quickly with H2O2. Considering the Mössbauer data, we conclude, in conjunction with the other spectroscopic data available and with the results of density functional calculations on related models, that this species corresponds to a high-spin side-on peroxo−Fe3+ complex. This is one of the first examples of such a species in a biological system for which Mössbauer parameters are now available: δ/Fe = 0.54 (1) mm/s, ΔE Q = −0.80 (5) mm/s, and the asymmetry parameter η = 0.60 (5) mm/s. The Mössbauer and spin Hamiltonian parameters have been evaluated on a model from the side-on peroxo complex (model 2) issued from the oxidized iron center in SOR from Pyrococcus furiosus, for which structural data are available in the literature Yeh et al. (2000) Biochemistry 39, 2499−2508. For comparison, similar calculations have been carried out on a model derived from 2 (model 3), where the CH3−S1- group has been replaced by the neutral NH30 group Neese and Solomon (1998) J. Am. Chem. Soc. 120, 12829−12848. Both models 2 and 3 contain a formally high-spin Fe3+ ion (i.e., with empty minority spin orbitals). We found, however, a significant fraction (∼0.6 for 2, ∼0.8 for 3) of spin (equivalently charge) spread over two occupied (minority spin) orbitals. The quadrupole splitting value for 2 is found to be negative and matches quite well the experimental value. The computed quadrupole tensors are rhombic in the case of 2 and axial in the case of 3. This difference originates directly from the presence of the thiolate ligand in 2. A correlation between experimental isomer shifts for Fe3+ mononuclear complexes with computed electron densities at the iron nucleus has been built and used to evaluate the isomer shift values for 2 and 3 (0.56 and 0.63 mm/s, respectively). A significant increase of isomer shift value is found upon going from a methylthiolate to a nitrogen ligand for the Fe3+ ion, consistent with covalency effects due to the presence of the axial thiolate ligand. Considering that the isomer shift value for 3 is likely to be in the 0.61−0.65 mm/s range Horner et al. (2002) Eur. J. Inorg. Chem., 3278−3283, the isomer shift value for a high-spin η2-O2 Fe3+ complex with an axial thiolate group can be estimated to be in the 0.54−0.58 mm/s range. The occurrence of a side-on peroxo intermediate in SOR is discussed in relation to the recent data published for a side-on peroxo−Fe3+ species in another biological system Karlsson et al. (2003) Science 299, 1039−1042.
•H. undatus and citric acid are green inhibitors.•The antiscalant properties were tested by using FCP and chronoamperometry.•The scale inhibition effects in solution and on a surface have been ...examined.
In this paper, the inhibiting properties of an aqueous solution containing Hylocereus undatus towards CaCO3 formation were studied by using fast controlled precipitation and chronoamperometric methods, in order to study the calcium carbonate formation in solution and on a metallic surface, respectively. As a purpose of comparison, the antiscaling properties of citric acid were studied in the same experimental conditions. The results obtained by fast controlled precipitation method showed that Hylocereus undatus solution was more efficient than citric acid to inhibit CaCO3 formation in solution (optimal concentrations of 20 and 24 mg L−1, respectively). By using the chronoamperometric method, a concentration of citric acid at 160 mg L−1 was required to totally prevent the precipitation of CaCO3 whereas it was 180 mg L−1 for Hylocereus undatus solution. The morphology analysis by scanning electronic microscopy and X-ray diffraction revealed that vaterite was favored in the presence of Hylocereus undatus solution, whereas a mixture of calcite and vaterite was obtained with citric acid.
This work deals with the inhibition of the scaling capacity of Hamma Bouziane (HB) groundwater (Algeria). In this study, the scale inhibition efficiency of gallic acid on calcium carbonate formation ...was assessed using chronoamperometry and impedancemetry. Owing to its characteristics of non‐toxicity and biodegradability, gallic acid can be classified as a green inhibitor. The obtained results showed that the addition of 1 mg/L of gallic acid to HB water significantly slows down scale formation, while the total inhibition of CaCO3 deposition needed only 4 mg/L. Thus, gallic acid proved to be an effective scaling inhibitor at very low concentration. The formed deposit was analysed by X‐Ray Diffractometry and Scanning Electron Microscopy. The results revealed that the predominant crystal structure is a mixture of calcite and aragonite in the presence of an inhibitor.
Chemical antiscalants are usually used to control scale depositions, a major concern in industry. Some of these products may be harmful towards environment or toxic for humans, so environmentally ...friendly antiscalant are needed. In this respect, plant extracts can be used as new green antiscalant agents. In this work, stock aqueous solution of Herniaria glabra (H. glabra) was obtained by infusion. H. glabra is used in traditional medicine to treat or prevent urolithiasis; it could be an interesting candidate as a green antiscaling agent. The properties of H. glabra towards CaCO3 formation were tested by using chronoamperometry and Fast Controlled Precipitation methods. An n-butanol solution was used to partition the aqueous solution of H. glabra, yielding a polar compounds-free fraction. This fraction was also studied by chronoamperometry and Fast Controlled Precipitation methods. The results showed a better inhibition efficiency towards CaCO3 precipitation for the n-butanol fraction compared to the crude H. glabra solution.
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•The antiscaling properties of H. glabra were tested by using FCP and chronoamperometry.•The solution of H. glabra was fractionated to isolate compounds of lower polarity.•Its inhibition efficiency was greater than that of the stock aqueous solution.
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