Ultrasound-assisted extraction of chromium from residual tanned leather: An innovative strategy for the reuse of waste in tanning industry

• Published in: Ultrasonics sonochemistry Vol. 64; p. 104682
• Main Authors: Bizzi, Cezar A., Zanatta, Raquel C., Santos, Daniel, Giacobe, Karen, Dallago, Rogerio M., Mello, Paola A., Flores, Erico M.M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-06-2020
• Subjects: Cr removal; Leather treatment; Process intensification; Residual tanned leather; Tannery industry; Ultrasound-assisted extraction; Cr removal; Tannery industry; Process intensification; Residual tanned leather; Leather treatment; Ultrasound-assisted extraction
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2019.104682

•Cr removal from residual tanned leather was feasible using ultrasound energy.•Efficiency higher than 92% was achieved for 30 min ultrasonication at 30 °C.•The proposed process is simple and fast when compared to the conventional process.•The UAE efficiency was at least 24% higher than that obtained with the use of mechanical stirring.•UAE process allowed Cr removal at milder operational conditions.
The tannery industry generates huge amount of waste with high Cr concentration, being classified as a dangerous waste. The development of alternative treatments for these residues aiming environmental friendly protocols are important topics of research. In this work, the use of ultrasound (US) energy for Cr removal from residual tanned leather was investigated. Ultrasound-assisted extraction (UAE) experiments were carried out in several systems as ultrasonic baths, cup horns, and probes, allowing to evaluate several frequencies (20–130 kHz) and power delivered to the extraction system. The following experimental conditions were evaluated: extraction solution (HCl, HNO3, H2SO4, CH2O2 and C2H2O4), temperature (10–90 °C), time (1–40 min), US amplitude (10–90%), feedstock amount (50–450 mg), and concentration of extraction solution (0.1–4 mol L−1). A multivariate factorial design with 10 axial points and 3 central points was applied. After UAE optimization an efficiency of 92% was achieved for Cr removal using 150 mg of feedstock, 3 mol L−1 HNO3, at 30 °C, 90% of amplitude, and 30 min. The same efficiency was not observed using mechanical stirring (100–500 rpm), which was lower than 65%. To prove the applicability of the proposed process some experiments for scaling up were performed using several reactor loads (1–9 L). Moreover, using the proposed UAE process Cr was efficiently removed at lower reaction time and at room temperature only by using US and diluted acid solution, representing energy and reagents saving.