Surface-Modified Nickel Foam Cathodes for the Electroflotation of Multi-Component Batik Wastewater

Wastewater from the batik textile industry contains diverse pollutants, including dyes, heavy metals, inorganic salts, and organic compounds, which are challenging to treat. Electroflotation has attracted increasing interest as a potential solution owing to its environmental friendliness and effectiveness against a wide range of pollutants. However, most previous studies have focused on improving electroflotation performance through anodic processes, while optimization of cathodic materials has received limited attention. In this study, nickel foam (NF) was investigated as a cathode material for the electroflotation treatment of batik wastewater. The NF cathode outperformed commercial electrodes due to its high electrical conductivity, large surface area, and low hydrogen evolution overpotential. Surface modification of NF via electrodeposition of nickel (NF/Ni) and nickel hydroxide (NF/Ni-OH) further enhanced electroflotation performance. Using an NF/Ni-OH cathode and a carbon rod anode in a NaCl electrolyte, the electroflotation process effectively removed dyes (Methyl Orange, 98.82%; Reactive Black 5, 99.87%; Methylene Blue, 97.75%), heavy metals (Cd, 58.7%; Cu, 45.3%; Zn, 91.4%; Cr-(VI), 9.3%), and silicate (21.0%) at - 0.8 V vs Ag/AgCl over 60 min. The removal mechanisms of dyes, heavy metals, and silicates were elucidated, and the large surface area of NF-based cathodes was shown to enhance hydrogen bubble generation and floc flotation, thereby improving pollutant separation. These findings indicate that NF-based cathodic electroflotation is suitable for the simultaneous removal of dyes, silicates, and heavy metals such as Cd, Cu, and Zn from batik wastewater under optimized conditions, with good reproducibility and reusability over repeated cycles.