Cuprous ion has wide applications in various industries due to its properties to form stable coordination compound of high solubility with different ligands. Compared to extensive R&D work on solvent extraction of cupric ion, the limited work is reported on cuprous ion extraction using organic extractant. Therefore, in the present work, solvent extraction studies have been carried out for the extraction of cuprous ion Cu(I) from chloride solution using extractant tri-butyl phosphate (TBP) diluted in 1-octanol, for application to recover Cu(I) from the etch waste of printed circuit boards (PCBs). Initially, the studies were carried out for the selection of suitable diluent to be used for Cu(I) extraction from chloride solution. The organic 1-octanol was found effective diluent for TBP. The behavior and reaction mechanism of TBP diluted in 1-octanol was also studied for the extraction of Cu(I) from chloride solution. Various process parameters viz. contact time, concentration of chloride ion, hydrochloric acid and extractant, temperature, etc., were also studied. The extractant TBP diluted in 1-octanol was found suitable for the extraction of Cu(I) from the waste chloride solution (containing both Cu(I) and Cu(II)) generated from the plant of PCBs manufacturing. The extraction isotherm plot indicates the requirement of two stages for the complete extraction of Cu(I). The studies revealed the formation of complex [CuCl2-center dot H+center dot TBP] in the organic phase. The extraction and stripping studies showed the suitability of the TBP diluted in 1-octanol for the recovery of cuprous ion from the waste chloride etch solution of PCBs. (c) 2008 Elsevier B.V. All rights reserved.