THIOUREA RECOVERY AND WATER SAVING FROM CdS-CBD EFFLUENTS IN CIS SOLAR CELL MANUFACTURING

摘要

CdS used as n-type heterojunction in CIS or CISe cells is almost always deposited by chemical bath deposition (CBD). This generates toxic effluents which must be processed or discharged. In case of discharge water may be recovered and the dissolved solids concentrated. Nanofiltration of thiourea (Tu) with Osmonics membrane shows an intrinsic rejection ratio equal to 0.85. This relatively low value obliges to use a cascade of modules (preferentially 3) in order to achieve the former objectives. Water recovery ratio higher than 80% may be achieved. Increasing recovery ratio induces an increase of Tu concentration in the water. Ion-exchange and activated carbon beds end the treatment and give high quality water (no detectable organic substance and conductivity less than 3μS cm{sup}(-1)).