The potential of date palm waste biochar for single and simultaneous removal of ammonium and phosphate from aqueous solutions

Abstract

Excessive amounts of NH4+ and PO43- cause eutrophication in water resources and harm the environment. The single and simultaneous removal of NH4+ and PO43- ions from aqueous solutions with different date palm waste biochar samples was investigated in batch and fixed bed column studies. The highest removal and adsorption capacities were 99.55% (49.76 mg/g) for NH4+, 51.53% (26.90 mg/g) for PO43- in single solution; 99.97% (48.74 mg/g) for NH4+, 52.42% (27.41 mg/g) for PO43- in mixed solutions at pH 7 with biochar pyrolyzed at 500 °C derived from the mixture of date palm leaves and fronds waste. The experimental data for NH4+ and PO43- fits well to the Langmuir isotherm model (R2 = 0.87–1) and the pseudo-second order kinetic model (R2 = 1) for single and mixed solutions. The increases in biochar bed depth and initial ion concentrations, and the decrease in the initial flow rate increased the exhaustion time, removal efficiencies, and dynamic adsorption capacities of both NH4+ and PO43- in single and mixed solutions. The maximum removal efficiencies and adsorption capacities were 82.22% (805 mg/g) for NH4+, 27.51% (92.78 mg/g) for PO43- in single solutions; 57.9% (165.17 mg/g) for NH4+, 31.56% (85.95 mg/g) for PO43- in mixed solutions. Regenerated biochar had still high removal efficiencies and adsorption capacities towards those ions. The NH4+ and/or PO43- ions adsorption on biochar samples were confirmed via Fourier transform infrared spectroscopy, Scanning electron microscopy, Energy dispersive X-ray and X-ray diffraction analysis.