Principle of the new sulfide method

System enabling to treat waste water with heavy metal and recover and recycle metal. This is the “new sulfide method (NS process)” which Aquatech boasts to introduce. By controlling feeding quantity of sulfidizing agent, NS process succeeds in overcoming the problems of offensive smell and colloidalization, from which conventional sulfide method suffered.

Characteristic of new sulfide method (NS process)

  • 1.Technology to control reaction by gas sensor
    (1)By monitoring generated gas, it is possible to precisely measure and control the terminal point of chemical reaction during treatment of waste water.
    (2)By feeding properly sufidizing agent, it is possible to prevent offensive gas from emitting
    (3)By feeding properly sufidizing agent, it is possible to prevent colloidalization.
  • 2. Reduction of sludge generated
    It is possible to reduce the volume of sludge to some one third of that of conventional process
    In case of nickel sulfide, water content is 10  20%.
  • 3.Reuse of recovered metal as resource
    It is possible to sell dehydrated cake as mineral materials because water content is low and mineral content is high.
    Example of operation: in case of dehydrated cake containing nickel: Nickel content is 30 -45% (dry base), Water content is 10 - 20%

Technology to control reaction by new sulfide method(NS process)

We have verified that there is a relationship as shown in the below diagram between progress of formation of sulfide in the solution containing metal ion and generating hydrogen sulfide gas.

How to control reaction of the new sulfide method (NS process)


In case the sulfide is precipitated according to formula (1) by adding sulfidizing agent to wastewater containing metal ion (M++), no hydrogen sulfide generates in the reaction tank as long as metal ion remains even if pH is low. This is because reaction (1) precedes reaction (2). Hydrogen sulfide occurs after the density of metal ion becomes sufficiently low as the precipitate formation proceeds. Based on this fact, we have succeeded in inventing a method to control sulfide to be fed and thus to control precisely and stably the process of precipitation of sulfide.

NS process features not only in its excellent treatment capacity of wastewater with heavy metals but also in its wide applicable fields. Please find below the metals which NS process can treat and industrial categories to which the process can be applied.

Metals treatable

NS process can treat many types of metals as conventional hydroxide precipitation method can.

  1. You can sell recovered sludge of Ni, Cu, Mo, Co, Sn, Au and Ag .
  2. You can use the system to recover rare metals and rare earth metals.
  3. NS process is far superior to hydroxide precipitation method in the treatment of poisonous metals like Pb, Hg, As ,Cd ,Se and Sb so as to reduce substantially their content.

Industrial segments applicable

It is applicable to a wide range of industrial segments including companies treating industrial wastes and research laboratories.

Industrial segments applicable Metals treatable
Company to treat industrial wastes Cu, Ni, Mn, Zn, Cd, Pb, Fe, As, etc.
Automobile industry Zn etc.
Surface treatment of metals (including plating industry)
Ni, Cu, Sn, Pb, Zn, Cd, Se and Ag,
Battery manufacturer Pb, Cd, Ni and Co,
Industry of catalyst and catalyst regeneration Pt,)Ni, Pb, Ir and V /td>
Metal processing industry Cu and Zn
Glass industry Pb)
Inorganic pigments industry Pb(and Cd
Non-ferrous smelting industry Cu ,Ni etc
Rare metal industry Ni, Mo, Co, Se, Sb, V and As
Pickling of stainless Ni and Fe
Pickling of stainless Manufacturer of electronics parts / machine parts Cu, Ag, Sn and As
Power station Ni, V, and Se
Incinerating plant Hg, Pb, Zn etc.
Fly ash treatment Hg, Pb, Zn etc
Earth friendly cement Cu, Zn etc.
Repairing site of contaminated soil Pb, Hg, Cd, As etc.
Labortory Hg(etc.)

As to separate recovery

NS process features in its ability to roughly separate and recover metals when wastewater contains plural metal ions. In principle, since the stable region of each metal sulfide differs depending on pH as the below diagram shows, it becomes possible to roughly separate and recover metals basing on the reaction caused by changing the pH.

As to separate recovery

As to small-sized test equipment

We undertake a continuous-typed or batch-typed on-site test by use of small-sized test equipment as well as beaker test at a laboratory (on paid base). Please feel free to ask us about more information.

Technology to recover metal in waste water