Decoloration by nanofiltration of effluents containing fountain-pen inks: Pilot scale qualification - Industrial assessment

The study deals with the treatment, by nanofiltration,of effluents generate d after rinsing the vats used for the manufacture of inks (pen cartridges). The first part of the study (bibliographical) shows that membrane processe s are operational in different industrial areas for the decoloration of eff luents but the number of nanofiltration plants is still limited. In the sec ond part (experimental) two tubular organic membranes (Koch-Weizmann MPT20 an MPT31), selected according to their molecular weight cut-off (450 dalton ) and their resistance to solvents and acid solutions. are performed and co mpared. The study shows that performances (i.e, permeation flux and retenti on late) of MPT20 membrane are linked noticeably to hydrodynamic parameters (pressure. velocity). Furthermore,for the two membranes tested the transpo rt mechanism across the medium is typically diffusional. The studies, at th e laboratory scale, conducted for a first time at constant solute concentra tion thereafter in a 'concentration mode', were followed by pre-industrial and long-term runs. The 3 weeks continuous experiments were found to be ind ispensable for the selection of the most suited membrane. Finally, the MPT3 1 membrane exhibited the best performances (no drift in flux nor alteration of selectivity with time). Under the operating conditions - 25x10(5) Pa, 2 .5 m.s(-1), 30 degreesC - the following performances were obtained:flux 41 l h(-1) m(2), decoloration > 99 %, COD divided by 4, volumic reduction > 10 , easy cleaning. This study has allowed the design and economical evaluatio n of an industrial equipment (running in France since February 1997) which is probably the first nanofiltration plant for this type of application in Europe.