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Zn-Co layered double hydroxide-based capacitive systems for removal and recovery of phosphate from aqueous environments
Journal
Colloids and Surfaces A: Physicochemical and Engineering Aspects
ISSN
09277757
Date Issued
2024-06-20
Author(s)
Choudhary, Vaishali
Abstract
The poor efficiency of traditional carbon electrodes in recovering phosphate from wastewater has led to the exploration of intercalated energy storage materials. Accordingly, the performance of Zn-Co layered double hydroxide (LDH) intercalated with chloride (Zn-Co-Cl), nitrate (Zn-Co-NO3-), carbonate (Zn-Co-CO32-) and synthesized by urea hydrolysis (Zn-Co-U) was examined for electro-assisted phosphate recovery. Structural characterization established that carbonate intercalated LDHs had the highest thermodynamic stability. The electrochemical characterization revealed high specific capacitance (380.8–573.5 F/g) of Zn-Co LDHs, with the primary charge storage mechanism as surface-controlled charge transfer. At an applied potential of 0.8 V, the phosphate electrosorption capacity was 59.4 mg P/g, 101.8 mg P/g, 44.8 mg P/g, 269 mg P/g for Zn-Co-Cl, Zn-Co-CO32-, Zn-Co-NO3-, and Zn-Co-U, respectively. The high electrosorption capacity (85.2%) and almost complete recovery (98.6%) of phosphate was demonstrated by Zn-Co-U for 20 cycles. The electric double layer and pseudocapacitive nature of the LDHs resulted in phosphate uptake via electrostatic attraction, ligand exchange, intercalation, and de-intercalation. The energy consumption for phosphate recovery using Zn-Co-U electrodes was minimal (0.02 kWh/g P). Overall, this work validates the effectiveness of pseudocapacitive materials like Zn-Co LDHs in achieving easy and reversible phosphate capture.
Volume
691
Subjects