With the increasing tense of water resource and the continuous improvement of the environmental requirements, industrial water treatment will face more and more severe challenges. The development and application of technologies, which include water treatment agent, membrane water treatment with water reuse, high concentration rate of operation and low phosphorus, even without the phosphorus biodegradable will become the focus of the development of water treatment technology for a period in the future.

Water treatment chemicals belong to fine chemicals. As the main products of water manufacturing and high-tech industry, silicon wafer occupies an important position in cooling water of phosphorus, which is widely applied in industrial cooling water circulation, boiler water, drinking water, industrial water, oil water treatment, etc. to achieve water conservation, rational water use and the purpose of water pollution.

Among them, the most common corrosion inhibitor is the organic phosphates and water-soluble polymer, and performance, environment, safety and price are four mainly decided factors of its application. Organic phosphates becomes the backbone of the composite reagents in water treatment by the excellent performance salt such as the good thermal stability and chemical stability, the suppression of crystal growth; Water-soluble polymer with good dispersion properties of organic phosphates and stability of calcium becomes particular active research direction in recent years.

1.1   Water-soluble polymer

      Water-soluble polymer developed from the initial Homopolymerization content into binary ternary copolymer, even the pluralistic copolymer gradually. Homopolymerization (such as polycryclic acid and gather the carboxylic acid) contains Malay functional and high molecular weight has excellent suppression to calcium carbonate, which provides the basis for cooling water treatment technology. Because cooling water must also be taken into account of the ferric oxide, calcium phosphate, clay particles suspended, such things of simple homopolymerization cannot satisfy the effect of cooling water treatment, so people mixed maleic acid or containing hydroxyl with amides, sulfonic acid, phosphonic acid, functional monomers, and obtained a series of binary ternary copolymer. So the comprehensive performance of polymers have greatly improved, such as acrylic esters acrylate copolymer) - (AA) / acrylic acid, - methacrylate copolymer (AA/MA), acrylic - 2 - acrylamide - 2 - methyl isopropyl sulfonic acid copolymer(AA/AMPS), acrylic - styrene acid copolymer (AA), HPAS/acrylic - vision propylene phosphate copolymer (AA/IPPA).  Especially the development of AA/AMPS copolymer in the 1980s was widely applied by its superior performance of dispersion.

With the strengthening of human environmental awareness, environmental friendly and strengthening the biodegradable efficient green corrosion inhibition becomes the key of the research development. The American company, Donlar’s development of aspartic Acid (PASP = polyasparticacid) in the early 1990s and Michael. Jennings Bryan’s invention of epoxy succinic Acid (PESA = Polyeproxysuecinic Acid) in the 90’s of 20th century all belong to such structures. Here is the structure:

Gather l-aspartic acid molecule does not include phosphorus, but has biodegrade ability and good performance of anti-scaling scattered .And it has been proved to have good corrosion properties in oil. Consequently, Donlar Company also has gained the “presidential green chemistry prize” in 1996. It shows that the best inhibition ranges of relative molecular mass, PASP on CaCO3, CaSO4, BaSO4 are 2000 ~ 5000, 1000 ~ 4000, 3000~ 4000 after comparing different production technique, relative molecular mass of polyaspartic’s acid resistance performance. Relative molecular mass of aspartic acid is better than polyacrylic acid in scale inhibitors, and the manufacturing process of reactants, clean and harmless, thus it has a good application prospect in the seawater desalination, pure water treatment and water-cooling disposal etc. In the early 1990s, Japan Kao Corporation and America Betz laboratory successively developed PESA (poly epoxy succinic acid) which is a kind of corrosion and scale inhibitors double function in polymer and is more outstanding in corrosion inhibition. Because molecules contain polyether and carboxyl and have good adsorption for all of the scale and the wall, consequently, it can provide good corrosion and scale inhibitors. Under the same conditions, the inhibition rate is much higher than polyacrylic acid and Malay high acid and has small toxicity, good biodegradable performance that can be accepted by the environment. PESA has the best performance within the scope of the relative 400-800 molecular mass, and its inhibition of calcium carbonate suppression is better than HEDP and the polyacrylic acid and inhibition of barite is obviously higher than hexametaphosphate.

1.2   Organic phosphate inhibitor

The organic phosphorus corrosion inhibitor is the most widely and successfully used chemical in industrial water treatment. This is because of their conditions in water treatment chemical stability and being used together with other water treatment in certain conditions, it can show ideal synergy and the results of corrosion inhibition effect.

The development of organic phosphonate experienced several generations. The first generation of organic phosphate anti-scaling inhibitor appeared in the 1960s, including hydroxyl ethyl fork 2 phosphonic acid (HEDP) and amino acid (alkylphenylphosphino) sanya ATMP) and ethylenediamine and methyl phosphonic acid (EDTMP), which all have the features of chemical stability and resistance to high temperature and high pH value, obvious synergy effect and dissolve limit, etc. They have excellent chelating ability to Mg2 Ca2 + to + +, and Zn2 Fe2 +, and many other metal ions, so they have strong inhibition to inorganic salt, especially CaCO3 and a certain corrosion inhibition, which got widely used. However, because their relative molecular mass and functional groups of calcium ions are smaller, theirs tolerance to calcium is not high, they cannot effectively restrain calcium phosphate, zinc and scattered iron scaling. Especially in high calcium ions and in water of iron ions, it is easy for it to form organic phosphate calcium and iron, which affects its usage. Its corrosion and scale inhibitors abilities are limited, so they are restrained in high concentration ratio in the treatment of cooling water.

In the 1970s, people developed the second generation of organic phosphate anti-scaling corrosion inhibitor, which mainly contains divinyl three amine five methylene group phosphonic acid (DTPMP) and three amine five methylene group phosphonate BHTMP. Their corrosion inhibition ability has been improved, but it also did not solve the problem of low tolerance to calcium ions.

1.2.2       phosphonate type compounds with carbon

HEDP (Hydroxy ethylidene diphosphonic acid) of phosphonate type compounds with carbon is one of earlier developed and used chemical in water treatment. The C- P bond in these compounds is more resistant to oxidation than N-C-P bond, its antioxidant properties is better than methylene phosphine acids compounds type. Similarly, it can form multi-ring chelate with Ca2 +, Mg2 +, Zn2 +, Fe2 + and other metal ions of water , so in addition to calcium carbonate, but also has a better inhibitory effect on the hydration of iron oxide and calcium phosphate, and also has good corrosion inhibition of carbon steel in water. Based on preparation of HEDP, many countries did a significant amount of research on synthesis processes of 1 - aminoethane -1, 1- diphosphonate (AEDP), proves their strong corrosion inhibition performance than HEDP. In the 1980s, America Betz company developed hydroxyl c fork 2 phosphonate (HPDP) and found that although the molecular structure of HPDP only increased one carbon atom than HEDP, but the Ca2 + inhibitory ability greatly exceed HEDP, and it can effectively prevent the calcium carbonate, calcium phosphate, calcium sulfate from forming in cooling water. At pH 9, it can allow the concentration of Ca2 + in the cooling water reaches or exceeds400mg•L-1(count by Ca2+).

1.2.3chiral carboxylic acids compounds

There are three carboxyl groups and a phosphonate in molecules of 2 - phosphonate butane - 1,2,4 - three carboxylic acid (PBTCA), which have  strong ability of chelating metal ions, showing strong corrosion and scale inhibitors. East China institute of chemical laboratory and Nanjing chemical industrial institute did system reaearch in the synthesis and applications of PBTCA, which shows that PBTCA has the effect of acid-resisting, alkali-resisting and antioxidant. Even when the pH value is more than 14, it still do not happen hydrolysis, good thermal stability, its inhibition performance in high hardness and high temperature is better than HEDP, ATMP. It is a kind of cathode corrosion inhibitor. American Geigy Ciba - developed hydroxyl phosphonic acid, acetic acid (HPA), better than molybdenum and zinc phosphate, is believed to be the most effective for black metal organic corrosion inhibitors.

1.2.4 the containing MPS organic phosphonate salt

Experiments show that the best stabilizers should has two functional groups, including strong acid to dissolve, and weak acid has adsorption ability of active part (restrain crystallization). From the Angle of acidic strength analysis, the acid is carboxylic acid. Therefore, the development of a molecule containing phosphonate and sulfonic acid, carboxyl functional organic compounds becomes people’s attention in recent years. Wujin fine chemical industry developed sulfonylurea unit such as amino dimethyl phosphine acids (SAPDP), its superior performance is better than HEDP and ATMP. Robert P Kreh [16] has developed a kind of corrosion inhibitor, formula as shown in figure 1-2: this potion soluble in water, can be applied to the pH value approximates 10 , hardness up for nearly 10 1000mg DE L - 1 high pH, high hardness of water.

1.3 macromolecular organic phosphonate

The structure and properties of organic compounds are closely related. It is one important way to prepare muti-function efficient corrosion inhibitor according to the function requirement and design target molecules that different functional groups coexist in the same molecular. If introduces the salt and organic phosphonate phosphonate group [PO (OH) 2] to polymer containning a variety of functional groups (e.g., esters, amides carboxylic acid and base, etc.), then can get a new molecular organic compounds with special structure and specific performance. Using all kinds of metal ions in the polar groups with strong chela cooperation and the high polymer dispersion, can not only ensure the effective performance of anti-scaling scattered, still can greatly improve the corrosion inhibition, corrosion and scale inhibitors. Then people begin to study and development the third generation of organic phosphonate, which has both character of polymer scale inhibitors of dispersant and phosphonate anti-scaling dispersant. The representative of macromolecular organic phosphonate corrosion inhibition is phosphonic carboxylic Acid (POCA) developed by American FMC Company and polyamino polyehter methylenephosphonate (PAPEMP) developed by Calgon Company in the 1990s.

1.3.1 Phosphine carboxylic acid

Phosphine carboxylic acid combines bisphosphonates and polymer together, which has the following structure:

The compounds were used in cooling water system of control deposition and erosion, table 1-1 is the performance comparison between POCA and other corrosion inhibition.

Table 1-1 shows, POCA have best affect on calcium carbonate, calcium phosphate scale inhibition, dispersion and particles of iron metal corrosion and higher tolerance of calcium. POCA on the ability to inhibit CaCO3 more or less the same with PBTC, and is similar to ternary copolymer sulfonic acid corrosion in controlling of calcium phosphate, dispersing iron, stabilizing zinc. It is a multipurpose water disposal reagent.

1.3.2 Amino polyether phosphonic acid methyl clay

Many amino polyether phosphonic acid methyl of clay structure is combination of organic phosphonate salt and polymer structure, as shown in figure 1-3:

Table 1-2 and table 1-3 show that PAPEMP is a fine calcium carbonate and calcium sulfate inhibitors, which with high calcium tolerance. Its resistance capacity of calcium scale is better than organic phosphonate and polymer, and good for silicon scale inhibition, and can be very good stablize iron, zinc, manganese oxide; corrosion performance is good, can solve in harsh conditions of corrosion and scale inhibitors. Especially suitable for high concentration ratio, has been used in water purification, such as the reverse osmosis and multistage braising system. Due to the excellent properties of PAPEMP, it has been applied soon in petrochemical industry, electric power, oil industries in abroad. Chinese He Gaorong and some other researchers did preliminary research on the application of PAPEMP and put forward the application of it in the development of the west to alleviate shortages to economic development in western pressure.

1.3.3 chiral carboxylic acids react together

In the 1970s, Geigy Ciba Company developed Phosphoric Carboxylic Acid (PCA), which is formed by inorganic Acid monomer monomers and other organic reactions. PCA is generally classified into two kinds, one is acrylic monomers used for basic peroxidase and sodium as the initiator and other monomers copolymerization, another is Malay acid monomer copolymerization and both have high capacity of calcium carbonate scale inhibition. Betz Company found that such PCA and AA / HPA inhibition after compound have synergistic effect on calcium carbonate, calcium sulfate, calcium phosphate and iron oxide dispersed sticky mud. Japan Hakuto Chemical Corporation found beudon phosphono polyacrylic acid and organic phosphates or organic phosphonic acid compound; there are clear synergies inhibitions. Mogul Company found in chiral acyl polyacrylic acid to CaCO3, Ca (OH) 2 (PO4) 6, especially MgSiO3 have certain ability to dissolve. Kelviny Chang et al in the high-pressure vessel in the thermal stability of the PCA studies have found that at high temperature under high pressure a small amount of PCA decomposition, NMR results show that the fragments containing the PCA in a variety of functional groups, still maintain the PCA of the dispersion and solubility.

Not only in room temperature, atmospheric pressure, PCA with good performance, even in high temperature, high pressure, its performance can also get well maintained. PCA is a good scale inhibition and dispersion agent, and has a capacity of dissolved iron oxide, phosphonic acid greatly improves the ability of polymer to iron chelation, makes the polymer dispersion of iron oxide with excellent performance. The molecular weight of PCA has some influence on its performance, comparing a wide range of molecular weight has high scale inhibition and dispersion. PCA as a polymer, not only contains phosphoric acid group, carboxylic acid groups, but also add a sulfonic group. Water treatment chemicals polymer containing sulfonic group compared to other polymers with high resistance properties of calcium phosphate, phosphoric acid groups to join the resistance to calcium phosphate polymer and further enhance performance. In the 1970s, Nalco Company began to study maleic phosphonic acids, became active again in the 1990s, and successfully used polymer in the oilfield water treatment. In the late 1980s, Japanese Kao Corporation for the polymer is discussed in detail, and the research result shows that its corrosion-proof scale-preventative agent performance is better than polyacrylic acid and Malay acid.

From the above review, organic phosphates organic phosphates by increasing the molecular weight, or the introduction of ether, sulfonic functional groups to improve their performance; and water-soluble polymer through the introduction of phosphoric acid, sulfur acid-based, etc. to improve the performance of its scale. Thus, two from different angles, along the direction of their walk get a crossing point- macromolecular organic phosphate, which provides a new and effective idea in inhibitor development. As PBTCA, in such a small molecule (M is 270) containing a chemical structure similar to acrylic acid, maleic acid and a phosphoric acid, which the other side of the macromolecular organic phosphates in the performance of explained.

1.4   corrosion-proof scale-preventative agent mechanism research progress.

1.4.1       organic phosphonate anti-scaling mechanism research

(1)   the lattice distortion theory

Calcium carbonate scale is the crystal, its growth is in accordance with the strict order, by the positively charged Ca2 + and the negatively charged binding CO32-on collision with each other, according to a certain direction. Adding organic acid to water, they will be attracted to the activity of calcium carbonate crystal growth with the Ca2 + chelation inhibited the growth of the lattice to a certain direction, thus making the lattice distortion, i.e. the surface of crystal is surrounded by organic phosphonic acid molecules and lost activity, and this is the mechanism produces the threshold effect. Similarly, this effect can also prevent the precipitation of other lens. In addition, some of the compounds adsorbed on the crystal growth with the crystal lattice, so CaCO3 crystal lattice dislocations, in the scale layer formed in a number of holes, the interaction between molecules decreases, so that the hard scale soft, as shown in Figure 1-4. As the organic acid with low molecular mass, it is adsorbed on CaCO3 crystal growth point of activity disturbed the crystal growth to a certain direction, and thus causes severe distortion.

(2)   increasing the solubility of compounds into the dirt

Organic acid in water to dissociate the H +, itself into a negatively charged anion, such as the type (1-3) as follows:

These negative ions with Ca2 +, Mg2 + and other metal ions to form stable chelate, thus enhancing the precipitation of CaCO3 when grain supersaturation, an increase of CaCO3 solubility in water.

1.4.2       clustering of carboxylic acid anti-scaling and dispersed mechanism research

(1) Solubilization

This statement similars to organic phosphonate can improve the solubility of of compounds, namely clustering similar carboxylic acid soluble in water, after the ionization negatively charged molecules, such as chain (4-1).

These negatively charged chains with Ca2 + to form water soluble complexes, thereby increasing the solubility of compounds into the dirt, play a role in inhibition

(2) Lattice distortion

As the polycarboxylic acid is a large molecular weight linear polymer, which adsorbed on CaCO3 crystal on one end, and the rest around the grain around, it cannot grow and become smooth. Therefore, grain growth is interfered and distorted; grain becomes smaller, the formed fouling layer is soft, easily washed away by water.

(3) electric double layer

Gill and others put forward electric double layer theory on the organic phosphonic acid scale inhibition effect. That the organic phosphonate scale inhibitors role is to spread the growth of nuclei near the boundary layer of concentration, the formation of electric double layer to the particle surface mutually exclusive, hinder scale ion or molecular clusters into the surface of metal together, showing scattered state of suspended fear Yu 3CBD3E 3A3D3C Yu 3CD? -5 follows: The mechanism is generally accepted speculation, the exact inhibition mechanism inhibitor also need to continue to study.

1.4.3 corrosion inhibition mechanism research progress

Study on the corrosion inhibition mechanism can be traced back to the early 20th century, and nearly three decades, research in this area is attracting the attention of scientists. In 1972, Fischer made a detailed analysis of different methods on the inhibition of corrosion electrode reaction, and proposed inhibition mechanism of the interface, electrolytic double inhibition mechanism of inhibition mechanism, membrane mechanism and the passive mechanism. Lorcns and Mansfeld [40] also pointed out that using interface and phase interface inhibition to express two different electrode reaction mechanism of block. They think that the role of interface inhibition occurred in the bare metal surface in contact with corrosive media between systems, and interface corrosion inhibition refers to the matrix and the electrolyte present in the same three-dimensional layer, the layer of corrosion products by a gentle micro-melting etching composition. Acidic solution mechanism of organic additives had already begun in the 1920s, which has started to get a new development in recent years. Scholars put forward the theory of adsorption and soft acid-base theory, modified theory and passivation theory, sophisticated catastrophe theory, etc. Of course, the focus and research point of above theories are different. In general, the acid medium is mainly adsorption-type inhibitor, the corrosion inhibition mechanism of a possible cover effect, while another possible mechanism for the negative catalytic effect. The so-called coverage effect is adsorbed at the metal surface, corrosion; metal dissolution process the anode and cathode hydrogen evolution process cannot be carried out. Negative catalytic effect refers to adsorption in the metal dissolution inhibitor activity areas, and its absorption change electrochemical process of corrosion anode cathodic reaction or activation energy, and thus blocks the process or the cathode to the anode process; perhaps even block the anode and cathode reactions. As the process of metal corrosion and corrosion complexity and diversity of corrosion inhibitor, it is difficult to explain using the same theory of the mechanism of various inhibitors. Below are some of the main points of corrosion inhibition theory.

(1) a film theory

Film theory is that the corrosion inhibitor forms a layer of difficult dissolved protective film on metal surface to prevent corrosion of the metal medium. The kinds of protective film include the oxide film and the deposition film.

(2) adsorption membrane theory

Adsorption membrane theory refers that some of the inhibitor molecules or ions through the metal surface physical adsorption or chemical adsorption protective film to inhibit the formation of the adsorption medium on the corrosion of metals. Some inhibitor molecules or ions and metal surfaces of electrostatic force and intermolecular forces and the occurrence of physical adsorption; other inhibitors can be used with the metal surface to form coordinate bond and a chemical adsorption. Inhibitor of its hydrophilic group adsorbed on the metal surface, away from the hydrophobic metal surface, forming adsorbed layer covering the metal active site to prevent erosion of the metal medium. Such inhibitors are mainly organic corrosion inhibitor.

(3) electrochemical theory

Electrochemical corrosion theory suggests that the cathodic corrosion process by increasing or decreasing the resistance of the anodic process of metal corrosion rate. Therefore, suppression is divided into anode and cathode inhibition and mixed type inhibitor. Corrosion is a complex process, usually through the formation of corrosion on the metal surface protective film two or three dimensions to achieve. There are many ways to study corrosion inhibitors and adsorption, according to the different underlying principles of corrosion products can be divided into analysis, electrochemical methods and spectroscopic methods. Corrosion products mainly based on analysis of the corrosion inhibitor adsorption, corrosion inhibition can cause certain change of macroscopic system of corrosion of metal objects (such as corrosion hydrogen or inhaled oxygen, temperature, etc.). The electrochemical method is based on the electrochemical corrosion inhibitor join change course, causing the corresponding chang of parameters (e.g., electrochemical corrosion and corrosion current density Ecorr potential Jcorr, polarization resistance and capacitance Cd Rp interface changes, etc.). Various technical requirements of modern spectroscopic methods can characterize the status of metal surface adsorption film and the fine structure, and thus determine the inhibition effect of corrosion processes and mechanisms.

1.4.4 organic phosphonate salt mechanism of polymer research progress

Practical significance of the larger organic phosphates must be connected to carbon atoms of two or more of phosphoric acid or phosphoric acid and other acid-based compounds. Only in this way, it has surface activity and the ability with metal ions to form a stable multi-chelate ring, shown in Figure 1-6.

Organic acid cannot become a single ring, so it does not have the feature of organic phosphates. Li Shouchun studied various amino acids (alkylphenylphosphino AAPA) and ammonia acid alkyl (AACA) of corrosion and scale inhibitors, ammonia alkyl phosphonic acid compound have better corrosion and scale inhibitors than the corresponding carboxylic acid alkyl ammonia compounds. The results further show that the number of phosphonic acid-based direct impact on the performance of this class of compounds containing two or more of phosphoric acid-based compounds that can show strong corrosion and scale inhibition performance. As the organic phosphates strong chelating ability, the inhibition mechanism on the one hand, through the formation of Ca2 +, Mg2 + multi-core polymer complex (debris) and discharge system, on the other hand it can be easily adsorbed on the crystal growth point on the scale inhibit the further growth of scale. Grabenstetter once studied in aqueous Ca2 + and HEDP4 - the complexes formed by the composition, as Ca2 + and HEDP mole ratio of 1 ~ 2, it can form [Ca (HEDP)], [2 - Ca3 (HEDP) 2] 2 - Ca4, [3] (HEDP) 4 - and Ca7 [4] (HEDP) 2 - as polynuclear complexes:

They can be scattered in solution, with the solution of the system with flow, and they can also be further polymerization into:

Type (1-5) in the large constants K0 indicates very easily aggregate. When the polymerization degree (n value) is large, it was settling down to form the soft dirt. Organic phosphonate salt is a steel and copper alloy corrosion inhibitors, and many of the corrosion mechanism is not completely understood, and formed on the surface of metal is closed and isolation performance of adsorption membrane on oxygen. For film composition is likely to be more than the metal surface nuclear complexes. Fang Jingli et al studied in the acidic conditions films formation properties of ATMP in the steel surface, found the formation of excellent corrosion resistance of passive film. Through the reflection infrared spectrum, Raman spectroscopy and photoelectron (XPS) study, and discussed the formation of the surface film is found by a kind of Fe2 + ATMP and forming complexes membrane. N, O of ATMP molecules has been involved in the coordination of the Fe2 + by Ar + etching curves obtained by film-forming regions constant elements as: O 48.4%, P 28.2%, Fe 6.2%, N 4.6%, C 12.6%, which is [Fe (ATMP) n] consistent with the composition. Similarly, the phosphonic acid compounds containing both phosphoric acid and the result of a carboxylic acid group they pass the metal ions in solution to form stable chelate, has excellent corrosion and scale inhibition performance. Wang Zumo et al studied on the photoelectron spectroscopy in neutral medium carbon steel surface PBTCA protective ingredients of morphology, elements of three-dimensional elements, distribution, and combination of atoms form etc. by scanning electron microscope, X-ray photoelectron from Russia, etc. The results showed that in neutral aqueous media, PBTCA mainly with divalent metal ions Ca2 +, Fe2 +, Zn2 +, etc. form a chelate form; when the dissolved oxygen and carbon steel surface iron atoms formed FeOOH, the complex with Fe (Ⅲ) complex precipitate formed covering the steel surface forms a protective film.

1.5 This thesis’s main work

The main work of this thesis is the use of Mannich reaction, the amino ether, phosphorus trichloride, formaldehyde at a certain temperature synthesis of new water treatment chemicals polyoxypropylene diamine tetramethylene phosphonic acid (DTPMP), its structure shown in Figure 1-7: n is 2 to 3, relative molecular mass of about 600.

With Fourier transform infrared (FTIR) and 31P nuclear magnetic resonance spectroscopy (31P-NMR) to determine the structure of synthetic products. By polarization curves and electrochemical impedance spectroscopy PDTMP to evaluate the corrosion performance, and its inhibition as the mechanism was discussed. And scanning electron microscope before and after adding corrosion inhibitor, carbon steel electrode in the acidic system (1 mol • L-1HCl solution) in the corrosion of the surface after 6 hours of scanning to observe the shape and characteristics of the adsorption films and further explained PDTMP inhibition mechanism and efficiency. By bubbling method and static anti-scaling method for PDTMP ATMP, DTPMP, the calcium carbonate scale PAA, performance evaluation, By static anti-scaling method for PDTMP ATMP, PAA, the resistance performance calcium sulfate, And static anti-scaling experiments produces scale sample separately scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis of several agents, and further discusses anti-scaling mechanism.