Futer of metal recovery technology

As gas sensor is a key device for new sulfide method (NS process) which Aquatech developed,so key technology
is to apply the sensor to controlling of reaction in liquid.Whi le technology develops every day,we must
sometimes wait from some years to some decades before seeing new technology accepted.Yet from now on
we will continue our effort to find
out new devices and to apply them to
the fields of waste water
treatment and recovery of


By marking in blue on periodic table, we show chemical elements on which we have certain level of knowledge through our past experience of operation as to treatment, separation and recovery.

Chemical elements on which we have certain level of knowledge

What is the best technology to separateEsolidify metal ion?

We show in the table below main metal ion separation methods from waste fluid/ fluid in process.
As to the question gwhat is the best method?h, the answer varies dependent on factors such as type of metal, density, type of coexisting ion, value of targeted metal, quantity of waste fluid or fluid in process and how to do with at later process.

Besides, there is combination technology, which provides various methods. We think it important to establish best system by comprehending individual method, its suitability to each waste fluid or fluid in process and confirming through small-scaled experiment, such as using beaker.

Method to separate metal ion in waste fluid or fluid in process

Treatment methodDetails of treatment method Principle
1.Coagulation method @‡@Hydroxide precipitation method@‡A Sulfide method@
‡BChelate feeding method
‡COxalate method
‡DCarbonate method‡EChloride method
Generation of insoluble salt
2DSolvent extractionSolution/solvent extractionSeparation by use of difference in solubility of two different solvents which do not mix
3.Ion exchange resin methodTower for positive ion exchange resin
Tower for chelate resin
Acid retardation
Ion exchange phenomenon
Separation of free acid from metal salt
4.Electrolytic deposition methodElectrolytic deposition (electrolytic bath pH control)To electrify anode and cathode placed in electrolytic solution and deposit metal on cathode
5.Crystallization method Heating / cooling equipment, chiller
Solid-liquid separation (centrifugal separator)
To cool and crystallize by use of difference in solubility according to temperature
6.Membrane separation methodRO etc.To condense metal salt by RO etc.
7.Cementation To add metal particle To extract targeted metal by difference in ionization


Future of gas sensor controlled sulfide method

As a treatment method of waste water containing heavy metal, hydroxide precipitation method in Table 1.‡@ above has been occupying almost 100% of the market for more than 100 years. In principle, sulfide method in ‡A is superior in removal and separation of metal, but due to two weak points - offensive smell and colloidalization, generally it has not been used and neglected except for some part of hydrometallurgy. Taking it rather as an opportunity to utilize the defect, Acuatech has succeeded in developing gsulfide method without offensive smellh by using gas sensor technology, which is recently remarkably developing. Many researchers and engineers acknowledge the superiority in sulfide method, but, from the beginning, most of them must have excluded the method from their subject of study as gdangerous and stinkingh. Meanwhile Aquatech thinks sulfide method will likely become a mainstream in future among technologies of separation and solidification of metal ion. Sulfidizing agent is not expensive because it is produced as byproduct of oil refining. Aquatech has treated by NS process the elements color marked in the table below. We think sulfide method does not necessarily suit to the treatment of elements marked in pale orange.

Metals applied the new sulfide method

Deployment from NEDOfs national project of research and development

So far, nickel sulfide sludge was considered stable, but recently NEDOfs research and development program, which Aquatech participates in, has succeeded in developing a technology to recover metal nickel with purity of over 98%. According to the process, first over 90% Nickel sulfide sludge is transformed to nickel sulphate sludge by airEbio oxidation in some 40 days and then nickel sulphate dissolves in water, becoming electrolyte with nickel content of some 10%, from which metal nickel is recovered by electrolytic analysis method. (PCT patent is filed)