Low-concentration palladium recovery from diluted aqua regia-based wastewater using lyophilized algal cells

• Published in: Resources, conservation & recycling advances Vol. 17; p. 200140
• Main Authors: Minoda, Ayumi, Miyashita, Shin-Ichi, Kondo, Takahiro, Ogura, Toshihiko, Sun, Jing, Takahashi, Yoshio
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2023
• Subjects: Acidic effluent; Adsorption mechanism; Biosorbent; Precious metal; Remediation; Wastewater treatment; Precious metal; XANES; Biosorbent; XPS; Remediation; SE-ADM; Wastewater treatment; Acidic effluent; Adsorption mechanism; XAFS; EXAFS
• ISSN: 2667-3789; 2667-3789
• DOI: 10.1016/j.rcradv.2023.200140

•Lyophilized G. sulphuraria cells recover Pd from diluted aqua regia with 6 M acids.•Lyophilized G. sulphuraria cells show high Pd-recovery efficiency and selectivity.•Pd accumulates in the peripheral region of lyophilized cells.•Pd forms an inner-sphere complex with the sulfur of the thiol group.•Pd was recovered from wastewater generated during printed circuit board production. Ion-exchange resins and activated carbons are used in waste refinement in the electronics industry to recover low concentrations of palladium (Pd) dissolved in diluted aqua regia (HCl:HNO3 = 3:1, v/v). However, these techniques are inefficient and have higher costs than benefits. Here, we showed that the lyophilized cells of the microalga Galdieria sulphuraria recovered Pd from 4 M acid-diluted aqua regia with < 135 mg L–1 Pd and 6 M acid solution containing < 50 mg L–1 Pd with greater efficiency than ion-exchange resins and activated carbons. X-ray absorption fine structure, photoemission spectroscopy, and electron microscopy revealed that Pd was adsorbed in the periphery of lyophilized cells by forming an inner-sphere complex with sulfur. Among other metals, G. sulphuraria could recover 97% of Pd from 5 M acid-containing aqua regia-based wastewater generated during the production of printed circuit boards. [Display omitted]