Overview
The removal of heavy toxic and metal ions like lead from wastewater is the most essential item that any industry needs to focus on. Especially in the case of industrial and mining waste effluents. In recent years, toxic waste treatment receives a lot of attention.We will be soon widely using in industries including metal plating, mining, tanneries, smelting, and alloy manufacture, among others. The goal of this study was to look into several ways for removing lead ions from industrial effluent.
Chemical precipitation, electrochemical reduction, ion exchange, reverse osmosis, membrane separation, and adsorption were all used to remove lead from industrial effluent. Technical applicability, plant simplicity, and cost-effectiveness are all important considerations for choosing the best treatment system for inorganic effluents.
About lead and how dangerous it is!
Lead is a soft, pliable bluish-grey heavy metal that rose to prominence due to its toxicity and ubiquitous occurrence in the environment.
It’s also a highly hazardous metal and a significant pollutant that enters the ecosystem via the soil, air, and water. If we use water without treating it for lead,then it may cause anaemia, kidney failure, brain tissue damage, and even death in certain cases! If lead is present in excessive concentrations, it can disrupt the environment and our ecology.
According to the World Health Organisation (WHO), the maximum permitted level of lead in drinking water is 0.05 mg/L. On the other hand, industrial wastewater have lead-ion concentrations of 200-500 mg/L, which is relatively high in terms of water quality regulations. Prior to discharge into water resources or sewage systems, the concentration of lead ions in wastewater should be lowered to a level of 0.05-0.10, on average. As a result, efficient treatment of industrial wastewater is critical. If we discharge this water without treatment, it can impact aquatic, terrestrial, and, indeed, the entire ecosystem! Many technologies have developed lead-removal systems to regulate wastewater contaminant limitation and reduce lead ion pollution.
To eliminate lead from industrial water and wastewater, we frequently use a variety of separation and treatment procedures. The industry must remember to consider the stream properties like lead concentration, pH temperature, flow rate, volume, and BOD in order to obtain the best potential results.
Precipitation:
The most popular method for eliminating lead ions from the water up to parts per million (ppm) levels is precipitation. Because the salts of lead ions are insoluble in water, precipitation occurs when the correct amount is introduced. Low pH and the presence of other salts reduce the efficiency of this process, which is cost-effective (ions). The procedure necessitates the addition of different chemicals, which results in the production of sludge with a high water content, which is costly to dispose of. At low concentrations, precipitation with lime, bisulfite, or ion exchange lacks specificity and is ineffective in removing lead ions.
Ion exchange:
Ion exchange is another technology for removing lead ions from effluents that have proven to be effective in the industry. Though it is more expensive than other approaches, it can attain ppb levels of clean-up while handling a significant volume. An ion exchange is a solid that may exchange cations or anions with the materials around it. We commonly use synthetic organic ion exchange resins as matrices for ion exchange. However, because the matrix is quickly polluted by organics and other particles in the effluent. Moreover, this technique has the disadvantage of not being able to handle concentrated metal solutions. Furthermore, ion exchange is a non-selective process that is extremely sensitive to the pH of the solution.
Electro-winning:
For heap leaching and acid mine drainage, electro-winning is widely being utilise in the mining and metallurgical industries. It’s also used to remove and recover lead ions in the metal processing, electronics, and electrical sectors.
Electro-coagulation:
Electro-coagulation is an electrochemical method for removing lead ions from a solution by using an electrical current. We can remove suspended solids, dissolved metals, tannins, and colors using an electro-coagulation method. Electrical charges keep the pollutants found in wastewater in solution. These ions and other charged particles become destabilized and precipitate in a stable state when they are neutralized by ions of opposite electrical charges provided by the electro-coagulation system.
Cementation:
Another sort of precipitation approach is cementation, which involves an electrochemical mechanism in which a metal with a higher oxidation potential enters the solution. We can also remove lead using this process.
RO and electro-dialysis:
The recovery of lead ions from dilute wastewater using reverse osmosis and electro-dialysis, which use semi-permeable membranes. We fit selective membranes (alternating cation and anion membranes) between the electrodes of electrolytic cells in electro-dialysis, and the associating ion migrates under continuous electrical current, allowing to recover the lead ions.
Membrane separation:
Membrane separation is a collection of physical separation technologies that remove particular constituents from a liquid stream using a permeable barrier. Due to advancements in system design and membrane materials, membrane separation technologies have surpassed traditional physical-chemical water treatment technologies. As a result, we can use them to remove hardness, colors, smells, and TDS, as well as heavy metals like lead. Membrane separation has a high rate of lead and other pollutant removal. This makes it an excellent choice for companies wishing to treat wastewater. They also help process water for reuse or those needing to meet rigorous lead or other heavy metals discharge regulations.
Bottom Line
We can determine the treatment options by effluent properties such as lead concentration, pH, temperature, flow volume, biological oxygen requirement, economics, and societal factors such as regulatory standards. Precipitation alone is rarely enough to lower lead concentrations to the levels required by water quality standards. Although these technologies are expensive, they also have various drawbacks. Drawbacks include the formation of sludge, poor percentage metal ion retention, high energy consumption, and low selectivity, making them unsuitable for small-scale enterprises.
As a result, adsorption is offered as a cost-effective and efficient strategy for retaining lead ions from aqueous industrial wastes. The most extensively utilized approach, however, is adsorption on the surface of activated carbon. Because it is simple, effective, and economical in removing heavy metals from an aqueous solution, adsorption is an economical and practical approach for retaining lead ions from aqueous industrial wastes.
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