Off - Site Recycling
Off-site recycling is a commonly used alternative for PWB manufacturers as a means of managing spent etchant solutions and wastewater treatment sludges. Widespread implementation of this option reduces the quantity of wastes being disposed of in landfills. The PWB survey gathered information regarding the types of wastes sent to off-site recycling firms, quantities, destinations, and associated costs. These data are presented and discussed in this section.
A summary of data related to off-site recycling of spent process solutions, including etchants, is presented in Exhibit 7-1. Nearly all respondents reported using off-site recycling for disposing of spent process baths. A summary of data related to off-site recycling and disposal of wastewater treatment sludges is presented in Exhibit 7-2. Nearly ninety percent (90%) of those who provided data concerning the destination of their sludges indicated that they ship the sludges to recycling facilities rather than landfills.
|279||cupric chloride||etch||11,000||gal||5.54||$/gal||Phibro Tech||40|
|279||cupric chloride||etch rinses||6,000||gal||5.45||$/gal||Phibro Tech||40|
|3470||gold plate bath||plate||60||gal||nr||-||nr||nr|
|6710||D001/D002||sulfuric/ peroxide||440||gal||1.96||$/gal||US Filter Rec.||40|
|6710||D002||ammoniacal etch||8,000||gal||1.52||$/gal||Phibro Tech||350|
|25503||cupric chloride||etch||2,000||gal||0.25||$/gal||Old Bridge||3,300|
|29710||D001||hot air solder lev.||1,482||lb||nr||-||Safety-Kleen||100|
|32482||gold plating||gold plate||100||gal||nr||-||Advanced Chem||120|
|33089||ammoniacal etchant||etch||60,000||lb||0.29||$/lb.||US Filter Rec.||225|
|33089||tin/lead||solder strip||6,000||lb||0.40||$/lb.||US Filter Rec.||225|
|37817||flux||hot air leveler||200||gal||230||$/drum||Entech Managt.||150|
|37817||acid sludge||waste catch drains||200||gal||230||$/drum||Entech Managt.||150|
|41739||D002||ammoniacal etch||17,000||gal||18,060||$/yr||Phibro Tech||400|
|41739||D008||solder bath||20,000||lb||nr||-||Alpha Metals||800|
|42692||ammoniacal etchant||etch||52,883||gal||nr||-||Old Bridge||400|
|42751||cupric chloride||inner layer etch||83,700||gal||nr||-||Norris Environ.||1,000|
|42751||ammoniacal etchant||outer layer etch||32,050||gal||nr||-||Phibro Tech||1,200|
|43694||ammoniacal etchant||etch||35,000||gal||nr||-||S. Cal Chem||30|
|43841||class 55||board scrap||38,000||lb||7,000||$/yr||SIMCO||1,000|
|44486||NH etchant||Cu etch||255,370||lb||nr||-||Phibro Tech||200|
|44486||peroxide/sulfuric||tin strip||49,911||lb||18,135||$/yr||Phibro Tech||200|
|44486||acid Ni||Ni plate||195||lb||683||$/yr||PhibroTech||200|
|237900||ammoniacal etchant||etch||50,000||gal||0.10||$/gal||S. Cal Chem||370|
|237900||acid||nitric solder strip||2,000||gal||4.60||$/gal||Norris||370|
|358000||etchant||etch||70,000||gal||0.11||$/gal||Old Bridge, NJ||600|
|358000||tin stripper||tin stripper||1,800||gal||3.18||$/gal||Republic||200|
|462800||spent copper||etch||1,419,393||lb||26,000||$/yr1||Phibro Tech||40|
|462800||acid rinse water||etch||349,020||lb||0.05||$/lb||Envirite||30|
|462800||copper sludge||etch/microetch||12,854||lb||0.00||$/lb||Phibro Tech||40|
|462800||spent flux||hot air leveling||4,400||lb||0.91||$/lb||AKA Industrial||55|
|946587||D002||Cu sulfate plating||7,500||gal||0.12||$/lb||Learonal||980|
|955703||solder oil||HAL solder||1,300||gal||0.40||$/lb||DK||20|
|955703||tin strip||tin strip||5,000||gal||0.37||$/lb||Phibro Tech||25|
|T1||ammonical etch||inner/outer etch||nr||-||nr||-||Phibro Tech||nr|
|T2||etchant||Cu chloride etch||18,500||gal||3.68||$/gal||Phibro Tech||7|
|T2||etchant||ammoniacal etch||33,000||gal||nr||-||Phibro Tech||7|
|T2||tin strip||tin strip||9,000||gal||3.45||$/gal||Encycle, TX||450|
|T2||nitric acid||rack strip||660||gal||4.09||$/gal||Encycle, TX||450|
|T3||etchant||etch||8,000||gal||nr||-||S. Cal Chemical||10|
|T3||nitric acid||rack strip||1,000||gal||5.36||$/gal||Great West. Chem||10|
nr = no response
Exhibit 7-1. Off-Site Recycling of Spent Process Fluids (continued on nest page)
|Quantity (lbs)|| Percent
|42692||200,000||40||unknown||85,000||0.43||S. Water Treat. Co||300|
|273701||300||50||D||200||0.67||US Filter Rec.||nr|
|36930A||181||50||D||nr||nr||US Filter Rec.||30|
|33089||80,000||35||D||48,000||0.60||US Filter Rec.||225|
|37817||1,000||95||R||1,500||1.50||NE Chemical Co||400|
2 Some variation in costs among respondents may be due to inclusion or omission of analytical fees (sometimes referred to as material profile fees).
nr = no response
Exhibit 7-2. Off-Site Recycling/Disposal of Wastewater Treatment Sludge
7.2 Off-site Recycling of Spent Process Baths
By far, the most commonly reported spent process fluid that is sent off-site for recycling is spent etchant, particularly spent ammoniacal etchant. Spent ammoniacal etchant is created at a rate of roughly 1 gallon per 30 surface square feet of inner- and outer-layer panels. On-site regeneration of ammoniacal etchant is not widespread. One respondent reported installing solvent extraction technology for the purpose of on-site regeneration of ammoniacal etchant and copper recovery in 1994 (see Section 6.2.4). The reason that spent etchant is a popular waste for off-site recycling is due mostly to its high copper concentration, which is typically 150 g/l Cu (i.e., 15% Cu). Etchant that is sent off-site is processed to recover the copper and regenerate the etchant for reuse. Eighty-three percent (83%) of the respondents who completed the off-set recycling section of the survey reported that they send spent ammoniacal etchant off-site for recycling. Costs associated with ammoniacal etchant recycling were provided in several different types of units and varied widely, but in general, it was clear that etchant recycling represented a major portion of overall recycling costs. One respondent (ID# 462800) reported an income from off-site recycling of their spent cupric chloride etchant ($26,000 annually).
Waste products other than etchant are less frequently sent off-site for recycling by the survey respondents. The next most commonly shipped waste product is tin and/or tin-lead stripping solutions. These solutions are listed by 20% of the respondents who completed this section of the survey form. Like etchant, spent stripping solutions have a high metal concentration that makes it a viable candidate for recycling. Also, stripping solutions are generated in relatively high volumes, furthering the economics of off-site recycling. For example, ID# 44486 reported shipping 49,911 lb of tin strip and ID# T2 reported shipping 9,000 lb of tin stripper). In comparison, these quantities are equivalent to approximately 20% to 30% of their etchant volume sent off-site.
Flux, solder dross from the hot-air-solder-level process, and other lead-bearing solutions are shipped off-site for recycling by 20% of the respondents. However, the quantities of these materials that are shipped are relatively small. One exception was ID# 41739, who reported shipping 20,000 pounds of solder bath to an off-site recovery facility. Tin-lead plating baths generally have a long life-span (several years) and disposal of the solution is an unusual event. For this reason, it is believed that with this particular case, shipment was a one-time event. For example, the facility may have replaced their tin-lead plating bath with a tin-only solution or needed to dispose of a bath due to irreversible contamination.
Micro-etchants are shipped off-site for recovery by only 8% of the respondents. Spent micro-etchants typically contain copper concentrations of 15 to 30 g/l Cu (i.e., 1.5 to 3.0% Cu). Other respondents reported electrowinning these solutions on-site, or treating them with conventional precipitation.
Gold- and silver-bearing wastes are sent off-site by 15% of the respondents. Gold electroplating baths (usually gold cyanide) have a long life-span, and not surprisingly, the reported volumes were all 100 gallons or less. Solutions containing gold may include spent gold electroplating bath, or the contents of drip or drag-out tanks on the gold plating line. Silver is present in film developing fluids that may be reclaimed on-site (electrowinned), shipped off-site for metal reclamation, or combined with other waste streams and treated conventionally.
Ten percent (10%) of the respondents indicated that spent rack stripping solution is shipped off-site. Plating racks are typically coated with a non-conductive substance to prevent electroplating from occurring on the rack surface itself. Due to use, this coating may degrade and plating can accumulate on the rack, especially near the clamps and contact points. This unwanted copper deposit is removed in a stripping solution such as dilute nitric acid. The volume of spent stripping solution can be significant. Respondent T3 shipped 1,000 gallons of nitric acid rack stripper off-site at a cost of more than $5 per gallon. By comparison, this volume is equivalent to 12.5% of the etch volume shipped by the same respondent.
7.3 Wastewater Treatment Sludge
A very high percentage of respondents (88% of those providing data) indicated that they send their wastewater treatment sludge to off-site disposal facilities rather than to landfills. This percentage appears to be particularly high when compared to the 31% of plating shops that use this method for disposal (based on results presented in ref. 1).
The average and median unit costs for off-site recovery of sludge are $0.48/lb and $0.21/lb, respectively. In general, the lower costs experienced by some respondents compared to others were due to larger-size shipments and shorter distances to the recycling sites, both of which reduce transportation costs. However, in some cases, differences in unit costs may be the result of other factors. For example, ID#'s 133000 and 953880 ship similar quantities of sludge the same distance to the same recycling company.m The unit cost of the off-site recycling for the two PWB manufacturers varies significantly ($0.17/lb vs $0.40/lb). One difference between the sludges shipped by these respondents is the percent solids. ID# 133000 is shipping a much dryer sludge (60% solids compared to 35% solids for ID# 953880). The dryer sludge will have a greater recovery value. By drying sludges PWB manufacturers can also reduce transportation costs since drying reduces the volume of the sludge. The sludge drying technology and its impact on sludge volume are discussed in Reference 1.
A discussion of off-site recycling, including descriptions of processes used by recycling companies, is presented in Reference 1.