This research is part of a continuing effort to reduce
environmental conflicts and occupational hazards of lead-bearing zinc
plant residues (ZPRs), and to break through this problem and recover
lead of the wastes. The residue with an assay of 14.4% Pb was used
in chloride leaching for lead recovery, and sulfate was controlled
in the leaching stage by the addition of Ca(OH)2. In this
paper, the effects of influential factors on extraction efficiency
of Pb from ZPRs were investigated. Taguchi’s method based on
orthogonal array design (OAD) has been used to arrange the experimental
runs in order to maximize lead extraction from a ZPR. Orthogonal array
(OA) L8(27) consisting of seven parameters,
each with two levels, was employed to evaluate the effects of NaCl
concentration (C = 300 and 400 g/L), stirring speed
(R = 500 and 700 rpm), reaction temperature (T = 55 and 65 ◦C), reaction time (t = 1 and 8 h), liquid-to-solid ratio (L/S = 6 and 20), acidic pH
(pHa = 2 and 3.5), and neutral pH (pHb = 4 and
5.5) on lead extraction percent. Statistical analysis, ANOVA, was
also employed to determine the relationship between experimental conditions
and yield levels. The results showed that the pulp density, and NaCl
concentration were significant parameters, and increasing pulp density
reduced leaching efficiency of lead. However, increasing NaCl concentration
promoted the extraction of lead. The obtained optimum conditions from
this study were C
2, 400 g/L; R
2, 700 rpm; T
1, 55 °C; t
1, 1 h; (L/S)2, 20; (pHa)2, 3.5; and (pHb)1, 4. But only
two significant factors (C
2, 400 g/L;
and (L/S)2, 20) were used to estimate the performance at
the optimum conditions. The calculated leaching percent (85.91%) was
in reasonable agreement with the experimental results in optimum conditions.
