Electrochemical sulfide removal and caustic recovery from spent caustic streams

Vaiopoulou, Eleni, Provijn, Thomas, Prevoteau, Antonin, Pikaar, Ilje and Rabaey, Korneel (2016) Electrochemical sulfide removal and caustic recovery from spent caustic streams. Water Research, 92 38-43. doi:10.1016/j.watres.2016.01.039

Author Vaiopoulou, Eleni
Provijn, Thomas
Prevoteau, Antonin
Pikaar, Ilje
Rabaey, Korneel
Title Electrochemical sulfide removal and caustic recovery from spent caustic streams
Journal name Water Research   Check publisher's open access policy
ISSN 1879-2448
Publication date 2016-04-01
Sub-type Article (original research)
DOI 10.1016/j.watres.2016.01.039
Open Access Status Not Open Access
Volume 92
Start page 38
End page 43
Total pages 6
Place of publication London, United Kingdom
Publisher IWA Publishing
Collection year 2017
Language eng
Formatted abstract
Spent caustic streams (SCS) are produced during alkaline scrubbing of sulfide containing sour gases. Conventional methods mainly involve considerable chemical dosing or energy expenditures entailing high cost but limited benefits. Here we propose an electrochemical treatment approach involving anodic sulfide oxidation preferentially to sulfur coupled to cathodic caustic recovery using a two-compartment electrochemical system. Batch experiments showed sulfide removal efficiencies of 84 ± 4% with concomitant 57 ± 4% efficient caustic production in the catholyte at a final concentration of 6.4 ± 0.1 wt% NaOH (1.6 M) at an applied current density of 100 A m−2. Subsequent long-term continuous experiments showed that stable cell voltages (i.e. 2.7 ± 0.1 V) as well as constant sulfide removal efficiencies of 67 ± 5% at a loading rate of 47 g(S) L−1 h−1 were achieved over a period of 77 days. Caustic was produced at industrially relevant strengths for scrubbing (i.e. 5.1 ± 0.9 wt% NaOH) at current efficiencies of 96 ± 2%. Current density between 0 and 200 A m−2 and sulfide loading rates of 50–200 g(S) L−1 d−1 were tested. The higher the current density the more oxidized the sulfur species produced and the higher the sulfide oxidation. On the contrary, high loading rate resulted in a reduction of sulfide oxidation efficiency. The results obtained in this study together with engineering calculations show that the proposed process could represent a cost-effective approach for sodium and sulfur recovery from SCS.
Keyword Electrochemical treatment
Sodium hydroxide
Spent caustic
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
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