Efficient removal of cadmium (II) and arsenic (III) from water by nano-zero-valent iron modified biochar-zeolite composite

Abstract

For the removal of Cd(II) and As(III) from water, this study synthesized a nano-zero-valent iron-loaded biochar-zeolite composite material (nZVI-BCZo) using a liquid-phase reduction method, with biochar, zeolite, and FeSO₄·7H₂O as precursors. The successful incorporation of nZVI onto the BCZo was verified through Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (FTIR) analyses, which revealed significant modifications in the surface oxygen-containing functional groups. Batch adsorption experiments were conducted to evaluate the adsorption characteristics and performance of nZVI-BCZo for Cd(II) and As(III). Under optimal conditions (pH 6.0, temperature of 310 K, and an adsorption time of 360 min), the maximum adsorption capacities for Cd(II) and As(III) were found to be 28.09 mg/g and 186.99 mg/g, respectively. The influence of pH on removal efficiency was more pronounced than that of temperature, with nZVI-BCZo exhibiting a higher affinity for As(III) compared to Cd(II). Kinetic analysis showed that the adsorption process is primarily controlled by chemical adsorption and follows a monolayer adsorption mechanism. Regeneration tests demonstrated that nZVI-BCZo retained good adsorption capacity after three cycles, with adsorption efficiencies of 67.78 % for Cd(II) and 53.04 % for As(III), indicating its potential for repeated use in water treatment applications. The economic evaluation revealed that nZVI-BCZo has a lower processing cost. Therefore, this study established nZVI-BCZo as an efficient, reusable, and cost-effective adsorbent for the treatment of heavy metal-laden water.