Determination of Optimum Conditions for Nano-Silver Preparation from AgCl Based on the Taguchi Design by the Use of Optical Properties of Silver

The Taguchi method, with L₂₅ (5⁵) orthogonal array, was used as the experimental design to determine the optimum conditions for the nano-silver preparation from AgCl via wet chemical reduction method. Ammonia solution, d-fructose, and poly­(vinylpyrrolidone) (PVP) were used as solvent of AgCl, reducing agent, and stabilizing agent, respectively. The UV–visible absorption spectra (abs) of silver nanoparticles were analyzed to optimize their optical properties including the wavelength of maximum absorption (λ_max), absorption efficiency (abs), and full width at half-maximum (fwhm), as well as the time of precipitation (<i>t</i>_p). The experimental conditions were studied in the range of 2–10 M for NH₃ concentration (<i>N</i>), 250–450 for [d-fructose]/[AgCl] (<i>F</i>), 6–54 for <i>W</i>_PVP/<i>W</i>_AgCl (<i>P</i>), 0–24 °C for reaction temperature (<i>T</i>), and 4–8 h for reaction time (<i>t</i>). The optimum conditions to obtain the minimum particle size or λ_max from this study were <i>N</i> = 2 M, <i>F</i> = 300, <i>P</i> = 54, <i>T</i> = 0 °C, and <i>t</i> = 4 h. Under these conditions, the optimum amount of λ_max was 365 nm. To maximize the abs, <i>t</i>_p, and minimize the fwhm while keeping the λ_max, three series of experiments, in alternative conditions, were performed. The total optimum conditions were <i>N</i> = 2 M, <i>F</i> = 450, <i>P</i> = 54, <i>T</i> = 6 °C, and <i>t</i> = 4 h, within the scope of the studied experiment

Determination of the Optimum Conditions for the Leaching of Lead from Zinc Plant Residues in NaCl–H₂SO₄–Ca(OH)₂ Media by the Taguchi Method

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 (<i>C</i> = 300 and 400 g/L), stirring speed (<i>R</i> = 500 and 700 rpm), reaction temperature (<i>T</i> = 55 and 65 ◦C), reaction time (<i>t</i> = 1 and 8 h), liquid-to-solid ratio (L/S = 6 and 20), acidic pH (pH_a= 2 and 3.5), and neutral pH (pH_b= 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 <i>C</i>₂, 400 g/L; <i>R</i>₂, 700 rpm; <i>T</i>₁, 55 °C; <i>t</i>₁, 1 h; (L/S)₂, 20; (pH_a)₂, 3.5; and (pH_b)₁, 4. But only two significant factors (<i>C</i>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