High-performance layered double hydroxide photoelectrocatalyst for sustainable water treatment: Accelerated tetracycline degradation and energy recovery

Abstract

Pharmaceutical pollutants are increasingly detected in wastewater, raising substantial concerns for the environment and human health. To tackle this challenge, we developed a layered double hydroxide (LDH)-modified BiVO₄ photoanode (ZnFe-LDH/BVO) for enhanced photoelectrochemical (PEC) degradation of tetracycline (TC-HCl). The ZnFe-LDH/BVO system demonstrated superior PEC performance, achieving a 0.066 min⁻¹ degradation rate, a photocurrent of 3.2 mA, and a 98% removal efficiency for 10 mg/L TC, surpassing bare BiVO₄, which achieved only 0.007 min⁻¹ and 1.6 mA. The ZnFe-LDH/BVO heterostructure effectively suppressed charge recombination, enabling a 9.5-fold increase in degradation rate compared to unmodified BiVO₄. The developed PEC system exhibited high efficacy in treating synthetic reverse osmosis concentrate (ROC) wastewater, where naturally occurring chloride ions were activated to generate reactive chlorine species, •Cl and •ClO, which facilitated efficient TC degradation. To further exploit the process, the system was also assessed for evolution of hydrogen, a useful carbon-free energy carrier, yielding H₂ production of 50 μmol/cm² in synthetic ROC after 2 h, compared to 4 μmol/cm² for unmodified BiVO₄. However, the presence of chloride ions also increased the potential for disinfection byproduct (DBP) formation, which was systematically evaluated under varying TC concentrations. Additionally, natural organic matter (NOM) in ROC solutions slightly inhibited PEC performance by quenching reactive species and adsorbing onto the photoanode, impeding TC-HCl oxidation. This study highlights the ZnFe-LDH/BVO PEC system as a promising technology for pharmaceutical degradation in wastewater, combining effective pollutant removal with potential energy recovery. Its robust performance underscores its practicality for sustainable wastewater treatment.

Graphical abstract

Keywords

Photoelectrocatalysis / ROC / BiVO₄ / ZnFe-LDH / Tetracycline / H₂ evolution

Highlight

	● ZnFe-LDH/BVO photoanode was fabricated via simple electrodeposition method.
	● ZnFe-LDH/BVO photoanode enabled highly efficient PEC degradation of tetracycline.
	● Reactive chlorine species boosted ZnFe-LDH/BVO PEC activity in ROC.
	● H2 evolution over ZnFe-LDH/BVO was over 12 times higher than bare BVO in ROC
	● The results for sustainable, dual wastewater treatment/H2 recovery were promising.

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