Rinse water Recovery System-METAPurefor recovery and reuse of electroplating rinse water.

Pure Tech India,A-5, Trec step, Thuvakudi, Trichy -620 015Telephone:00 91-431 320 6753; Telefax: 00 91-431 250 1100E-Mail: contact@puretechindia.com; website: www.puretechindia.com

Electroplating processes and various chemicals used:

S. No Plating process Major chemicals used

1 Cadmium plating Cadmium Oxide, Sodium Cyanide, Sodium Hydroxide

2 Zinc plating Zinc Oxide, Sodium Cyanide, Sodium Hydroxide

3 Copper plating Copper Cyanide, Sodium Cyanide, Sodium Hydroxide

4 Nickel plating Nickel Sulphate, Nickel Chloride, Boric Acid

5 Chromium plating High speed self regulating salt (Chromium sulphate, Chromic Acid)

Important Contributors in a Electroplating Effluent Generation:

Component Function Effluent Contribution/Remarks

Plating Bath Main component primarily responsible for plating. Contains bath chemicals.

Bath is not drained at all except for some unavoidable circumstances generally not seen.

Plating Rinse Removes excess coating material.

Major contributor of effluent. Contains primarily bath chemicals with some environmental contaminants.

Acid Bath and Rinse

To clean materials of rust. Bath and rinse becomes unusable after a particular period of operation. Main contaminants include rust material with some dust particles.

Alkali Bath and Rinse

To clean materials of rust preventive solutions, oil and grease for better plating efficiency.

Bath and rinse becomes unusable after a particular period of operation. Main contaminants include oil and grease, rust preventive solution.

Floor Washings

Spillovers from plating, rinse, acid and alkali tanks.

All effluents listed above in small quantities with water used for floor washing.

Treatment processes available:

• Chemical treatment using – Sulphuric Acid (pH reduction for chromium conversion)

– Sodium Bisulphite (used for converting hexavalent to trivalent Chromium)

– Sodium Hypo (Cyanide Oxidation)

– Lime/ Caustic (neutralization)

– Polyelectrolyte (flocculation)

– Clarification (solid- liquid separation) and– Solid sludge separation.

• Membrane based physical/physiochemical processes.

Conventional Treatment:

Electroplating Effluent

Oxidation/ Reduction/ Neutralization *

Neutralization

Precipitation

Flocculation (Polyelectrolyte)

Clarification

Sludge Storage

Dewatering

Disposal

Waste water discharge

* : NOTE

Cyanide waste: Oxidation

Chromium Waste: Reduction

Acid/Alkali Waste: Neutralization

Membrane Systems

An Overview

Filtration: Types and Comparison

Normal Filtration Cross- flow Filtration

• Normal Filtration: Water with contaminants pass in direction perpendicular to filter media. The contaminants will choke the pores of the filter media.

• Cross- flow Filtration: Water with contaminants pass in direction parallel to the filter media. The Outlet from this filtration will have two streams coming out. The concentrate stream will carry along with it the contaminants. The filtered water will come out of a separate outlet. The frequency of filter media getting choked is very low when compared to normal filtration.

Cross- flow Membrane Processes:

SS

Macromolecules

Sugar, DV Salts, DA

MV Salts, UA

MF

UF

NF

RO

Water

KEY:SS - Suspended solidsDV Salts - Divalent saltsDA - Dissociated acidsMV Salts - Monovalent saltsUA - Undissociated acids

Reject portion

Permeate portion

MF – Micro filtrationUF - Ultra filtration NF – Nano FiltrationRO – Reverse Osmosis

Specific advantages of membrane based treatment systems:

• Compact and less space occupying.• Marginal chemical consumption (needed in case of pH

correction).• Skid mounted systems.• Very low sludge generation.• Very low electricity consumption.• Requires little/ no civil construction.• Separated water is ideally suitable for high quality rinse

and bath top up.

Reverse Osmosis:

Finest form of filtration

Osmosis - Reverse Osmosis Illustration:

Concentrate Dilute DiluteConcentrate

Semi- Permeable Membrane

Semi- Permeable membrane is one which will allow only water molecules to pass and not salts.

In the Left diagram, under normal circumstances, water molecules from dilute solution side will permeate towards concentrate side to form an equilibrium.This is Osmosis and the pressure present is Osmostic pressure.

In the right diagram, when a pressure P is applied in excess to the normal pressure , water alone is squeezed into the dilute solution side from the concentrate solution side. This is Reverse- Osmosis.

Pressure P

Typical Reverse Osmosis Membranes:

Reverse Osmosis Process flow diagram:

RO membrane structure:

Separated components applications:

• Permeate flow (usable/product water flow) – Rinse– Bath top up

• Concentrate flow (Reject flow):-

– Bath (if the concentrate contains only salts used in the electroplating bath with permissible contaminants)

Reverse Osmosis Membranes Rejection Rates:

Solute Symbol Molecular weight Rejection (%)

Sodium Fluoride NaF 42 99

Sodium Cyanide NaCN (pH 11) 49 97

Sodium Chloride NaCl 58 99

Silica SiO2 (50 ppm) 60 98

Sodium Bi- Carbonate NaHCo3 84 99

Sodium Nitrate NaNo3 85 97

Magnesium Chloride MgCl2 95 99

Calcium Chloride CaCl2 111 99

Magnesium Sulphate MgSo4 120 >99

Nickel Sulphate NiSo4 155 >99

Copper Sulphate CuSo4 160 >99

Membrane based Rinse water recovery systems

Major contaminants and their removal:

S .No Contaminant Removal Process

1. pH Correction • Acid/ Alkali addition

2. Suspended Solids

• Stainless Steel Filter Strainer• Stainless Steel Bag Filter

3. Microscopic oil particles • Activated Carbon Filter

4. Coating Materials• IONICS unit using Reverse Osmosis membranes

Process Flow Diagram

Effluent from electroplating

process

Acid/ Alkali addition

Filtration System

High pressurepump

RO based IONICSUnit

Permeate tank to process

Pump

Reject back to bath/ treatment

Prep Tank

Low flow membrane systems:

High flow membrane systems:

A Typical application in electroplating process:Flow of parts

Stage 1 Stage 2 Stage 3 Stage 4

High Pressure Rinse

Chemical Cleaner

Spray-Dip-Spray

City Water RinsePhosphate Dip

Flow of parts

Stage 5 Stage 6 Stage 7 Stage 8 Stage 9 DI water Spray-Dip-Spray

City Water Rinse Chromate Dip Spray Rinse

Spray-Dip-Spray

Water Rinse

Spray Water Rinse

RO

TO WASTE TREATMENT

RO Process in Nickel Plating

feed

PLATE RINSE # 1 RINSE # 2

parts parts

RO

95%

recovery

concentrate permeate

Make-up

(Pure water)

evaporation

Benefits:• 70% of rinse water can be recovered and reused for Bath Top up

and as Rinse water.• Pollution Problem solved• The cost of treatment is got back to by way of water which can be

reused for rinsing process.

Customers:• Silver Crown Electroplaters: 100 and 200 LPH• Divya Engineering : 10 LPH• Sundaram Fasteners Limited, Chennai: 200 LPH

Other Electroplating Process related Products:

• Desorber: Oil water separator for Degreasing Baths.

• OleoSepa: Desorber, Ultrafiltration System for complete oil removal and reuse of Degreasing solutions.

• Bag Filtration System: For filtering suspended solids upto 1 microns for your plating baths. Filter media can be offered in Stainless Steel, Polypropylene and HDPE wire cloths. Complete unit can be fabricated in the above materials.

• RO Plant: For removing Total Dissolved Solids in water used for bath and rinse for better efficiency of plating.

Thank You

For Queries, Please contact:E- Mail:

contact@puretechindia.com(Photographs shown are taken from our supplied equipments

and there are feature additions taking place in each new equipment manufactured)