Manganese and nitrate removal from groundwater using date palm biochar: Application for drinking water

Abstract

This study investigates the removal of manganese and nitrate from aqueous systems in batch and column studies using date palm waste-derived biochar. High removal efficiencies and adsorption capacities (73.20%, qe: 3.57 mg/g for manganese and 94.94%, qe: 4.18 mg/g for nitrate) were attained at pH 6 with a dosage of 0.1 g biochar derived from a 50/50% mixture of date palm leaves and fronds pyrolyzed at 500°C. The equilibrium data fits well to the Freundlich and Langmuir isotherm models for manganese and nitrate respectively with R2=1. The Freundlich model dictates that the biochar's surface is heterogeneous, and manganese adsorption can occur in multiple layers. According to the Langmuir model, nitrate adsorption takes place on a homogeneous layer, and no interactions are fostered between the nitrate molecules on the adsorbent layer. The pseudo-second order model was found most suitable for both manganese and nitrate with R2 = 0.99 and 1, respectively. Results from the dynamic column study showed that increasing biochar bed depth and lowering the flow rate and influent concentration increased the removal efficiencies and adsorption capacities to 53.78 (qe: 8.54 mg/g) and 45.40% (qe: 4.39 mg/g) for manganese and nitrate, respectively. To confirm the adsorption of manganese and nitrate onto the biochar, physical and chemical characterization methods were used. The optimum conditions obtained from the dynamic column study were employed to study biochar efficiency to remove manganese and nitrate from synthetic groundwater in the presence of other cations and anions as field column study. The manganese and nitrate concentrations in the treated groundwater met World Health Organization drinking water standards.

Keywords

• Adsorption
• Date palm waste-derived biochar
• Groundwater
• Manganese
• Nitrate
• Fixed-bed column