There are biological leaching methods, phytoremediation methods, electrokinetic technology, acidification extraction methods, heavy metal passivation methods, etc.
1. The biological leaching method consumes less acid and has low operating costs. , highly practical, cost-effective, and a potential heavy metal removal method. However, the main bacteria used in the bioleaching method, such as Thiobacillus, proliferate slowly, the bioleaching retention time is long, and the effect is unstable.
2. Phytoremediation technology is affected by the geographical conditions of the soil to be treated. Different ecological plants must be selected for soil with different pollution conditions. One plant often only absorbs one or two heavy metal elements, which limits the It overcomes its shortcomings such as the treatment of soil contaminated by various heavy metals.
3. The advantage of electrokinetic technology is that it is low cost and can remediate a variety of pollutants. Electrodynamic technology has the characteristics of high efficiency and short operation time in purifying low-permeability soil and sludge polluted by heavy metals, organic matter, etc. However, so far there are very few domestic research reports on the basic principles of electrokinetic technology and its removal of heavy metal pollutants from sludge.
4. The acidification extraction method is to first use sulfuric acid, hydrochloric acid or nitric acid to adjust the acidity of the sludge to pH = 2, and then use complexing agents such as EDTA to separate the heavy metals. The filtration rate of this method can reach 96%, but it is difficult to apply in actual production due to problems such as huge investment, difficult operation and the need for a large amount of strong acid and quicklime.
5. The passivation method is to convert bioavailable dissolved and exchangeable heavy metals into other substances that cannot be utilized by plants
by adding passivating agents to the sludge. form. Although heavy metals have not been removed from the sludge, their biological effectiveness has been greatly reduced. By adding different modifiers or heavy metal passivators such as fly ash, phosphate rock powder and peat into sludge compost, the phytotoxicity of the compost can be greatly reduced, thereby reducing the availability of heavy metals in the sludge.