On-line Monitoring of Two-methods Complementary Instrument Market for Steady Growth of Heavy Metals

At present, there are two methods for on-line monitoring of heavy metals used in water quality: anode dissolution method and photometric method. There are many discussions in the industry about these two methods, but they are often not comprehensive and objective. Both methods actually have their own characteristics.

Spectrophotometry has its advantages. The method has good stability and convenient instrument maintenance. It has been applied very well in the monitoring of hexavalent chromium, total chromium, copper, manganese, nickel and other heavy metals; but at the same time it also has its limitations, such as the sensitivity of the method. Not high, the individual element detection selectivity is not strong, susceptible to co-existing ion interference. For example, the detection of lead and cadmium, photometry is based on dithizone reagent, the selectivity of the chromogenic reagent is not satisfactory, it responds to many metal ions, and the sensitivity is not enough, which can not meet the detection of low concentration of complex water samples.

The anodic stripping method is based on the electrochemical reaction of the electrode surface. The detection mechanism is more complicated than the photometric method. The method is also sensitive and the reproducibility is slightly worse than the photometric method. In addition, the technical requirements of the instrument maintenance work are also higher than the photometric method, especially the electrode grinding and maintenance. The maintenance engineer needs to be professionally trained and practiced for a period of time to be able to master it well. Although the anodic dissolution method has these deficiencies, its advantages are also very obvious. The method has high sensitivity and the detection limit is generally 0.1-0.5 ppb, which can meet the detection of low concentration water samples. The selectivity is good and the detection of lead, cadmium, and copper can be achieved at the same time. These advantages make up for the limitations of the photometric determination of heavy metals such as lead, cadmium, and mercury.

As to who is better or worse for heavy metal monitoring methods, it should be viewed more comprehensively and objectively. From the current technology point of view, the two methods have their own advantages and disadvantages, just to form a complementary, users can choose according to the specific application.

Instrument: The current market for heavy metal on-line water quality monitors seems to be relatively “silent” and is it likely to usher in market explosion in the future?

Xiang Guanghong: Combining the characteristics of the heavy metal online monitor market itself and the current market conditions, personally, it is inaccurate to say that the instrument market is silent.

On-line monitoring of heavy metals is not the same as conventional COD and ammonia nitrogen on-line monitoring. COD is a company that discharges sewage above the designated scale and has to monitor it. Therefore, the market capacity is large and it is relatively easy to estimate. Heavy metals are characteristic pollutants with obvious industry attributes. Emission companies are much smaller in number than COD emission companies. And there are also great differences in the types of heavy metals monitored by different industries. From the perspective of the industry and the promotion of market products in recent years, domestic pollution source heavy metal online monitors are mainly based on the monitoring of chromium and lead. In general, the market capacity of heavy metal online monitors is smaller than COD online monitors and ammonia nitrogen online monitors.

In fact, compared to three or four years ago, the installed capacity of heavy metal on-line monitors has increased significantly and the market has gradually become “hot”. However, because the market capacity itself is relatively small, even if the market is "hot", it is difficult to achieve the market scale like COD online monitor and ammonia nitrogen online monitor. So this gives people the feeling that this market is more "silent". In fact, the current market for heavy metal on-line monitors should have been on the right track, and the follow-up will maintain a steady and sustained growth trend.

Instrument: Some people think that "in the anodic stripping method, the use of less toxic helium instead of mercury as the electrode will lead to an increase in the detection limit and will interfere with the detection of some heavy metal elements (such as copper), affecting the accuracy. Too much application prospect." How do you see this view?

Xiang Guanghong: Any method has advantages and limitations. From the aspect of sensitivity, the helium electrode and the mercury electrode are equivalent, and there is no obvious difference. Both can reach the detection limit level of 0.1-0.5 ppb, but the helium electrode has no risk of mercury contamination with respect to the mercury electrode. Of course, the thorium electrode method also has its own limitations. The enrichment of the leaching potential of thorium itself overlaps with the copper element. When the concentration of copper ions in the sample is too large, it will compete with the helium, which will cause interference, which is what everyone proposes. The electrode is not suitable for applications where the copper concentration is high. From the perspective of technological development, helium electrodes are more environmentally friendly and safe than mercury electrodes. They can be used as a substitute for mercury electrodes as long as they avoid working conditions that are not applicable.

In view of the respective advantages and limitations of the two methods of helium electrode and mercury electrode, Concentration Technology has also developed two application schemes for helium and mercury electrodes. We will give recommendations based on the customer's working condition assessment. Under the premise of ensuring that the instrument is suitable for field applications, we will do our utmost to avoid monitoring the secondary pollution caused by ourselves.

Instrument: Please introduce concentrator heavy metal online monitoring related product line situation?

Xiang Guanghong: Concentration Technology released the first heavy metal on-line monitor in 2009. Currently, it has a detection platform based on the principle of photometry and anodic dissolution. The product based on the photometric method can monitor total chromium, hexavalent chromium, copper, Heavy metals such as zinc, nickel, and manganese; products based on anodic stripping can monitor heavy metals such as lead, cadmium, mercury, arsenic, and copper.

Instrument: In the face of many competitors, what is the market competitive advantage of your company's heavy metal online monitor?

Xiang Guanghong: In the face of numerous domestic and foreign competitors, we have improved our competitive advantage through multiple levels.

Spotlight's heavy metal online monitoring instrument uses the company's patented online sequential injection analysis platform. The reagents are very economical. The reagent consumption is about 1/5 of that of similar products. The monitoring frequency is 2 hours, and the 500ml reagent can satisfy 1 Used for months. At the same time, we also developed two kinds of technical platforms: photometric method and anodic dissolution method. The product range is complete. It has covered the heavy metal pollutants that are of major concern at the current stage in China and can meet various industrial applications.

At the same time, we attach great importance to the application of the product research, launched a large number of industry application research before the product launch, verify the applicability of the product for different working conditions in advance, and publish application programs in different industries, such as the elimination of sulfurous acid against hexavalent chromium monitoring The salt interference program aims at monitoring total chromium in tannery wastewater to eliminate high-concentration COD interference. Concentrating Technology can also customize different ranges, communication protocols, and system integration solutions according to customer needs, and can quickly respond to customers' special application needs.

In addition, concentrator's heavy metal online monitor uses a platform design, and the same technical principle of the instrument is exactly the same on the module. When customers want to adjust the monitoring target heavy metal pollutants for various reasons, they can switch to other heavy metal pollutants monitoring through software upgrades (sometimes need to replace the light source or electrodes) on the original instrument without changing. The instrument can greatly save the customer's investment.

Instrument: Can you provide some suggestions for the users of heavy metal on-line monitor instrument selection?

Xiang Guanghong: Heavy metal monitoring was developed only in the past two years. Users have limited knowledge of heavy metal monitoring technology and do not have enough experience. Different vendors may have a certain tendency for sales promotion. Therefore, the user is selected. Types will face many difficulties.

I hereby advise users to pay attention to the following points when selecting models: (1) We must fully understand and understand the advantages and disadvantages of the two methods of photometric and anodic dissolution methods; (2) communicate more with technical experts and understand the various brands. Product features; (3) Interact with units that have used such products and learn from their experience.