Abstract
In this study, date-palm biochar MgAl-augmented double-layered hydroxide (biochar–MgAl–LDH) nanocomposite was synthesized, characterized, and used for enhancing the removal of phosphate and nitrate pollutants from wastewater. The biochar–MgAl–LDH had higher selectivity and adsorption affinity towards phosphate compared to nitrate. The adsorption kinetics of both anions were better explained by the pseudo-first-order model with a faster removal rate to attain equilibrium in a shorter time, especially at lower initial phosphate-nitrate concentration. The maximum monolayer adsorption capacities of phosphate and nitrate by the non-linear Langmuir model were 177.97 mg/g and 28.06 mg/g, respectively. The coexistence of anions (Cl−, SO42−, NO3−, CO32− and HCO3−) negligibly affected the removal of phosphate due to its stronger bond on the nano-composites, while the presence of Cl− and PO43− reduced the nitrate removal attributed to the ions’ participation in the active adsorption sites on the surface of biochar–MgAl–LDH. The excellent adsorptive performance is the main synergetic influence of the MgAl–LDH incorporation into the biochar. The regeneration tests confirmed that the biochar–MgAl composite can be restored effortlessly and has the prospective to be reused after several subsequent adsorption-desorption cycles. The biochar-LDH further demonstrated capabilities for higher removal of phosphate and nitrate from real wastewater.
Highlights
Nitrate and phosphate are necessary nutrients for the growth of plants, wildlife, and humans
The adsorption capacity and interaction mechanism of the synthesized composite with phosphate and nitrate anions were evaluated in depth by considering isotherms, kinetics, and thermodynamic models
A negligible effect of coexisting anions on phosphate removal by biochar–MgAl was found due to the stronger bonds of Cl−, SO42−, NO3−, CO32− and HCO3− to surface sites of biochar–MgAl when phosphate and other anions coexisted in the water solution
Summary
Nitrate and phosphate are necessary nutrients for the growth of plants, wildlife, and humans. General sources of nitrate and phosphate contaminants in water bodies usually arise from the waste products of human activities such as discharges from industrialized practices, agricultural uses like inorganic fertilizers, compost, and wastewater treatment effluents [3]. Phosphates ions present in the water nourish algae, which further destroy other forms of life and yield unsafe contaminants. Excessive levels of nitrates are considered the main harmful waste for ground and surface waters, and pose a severe threat to the survival of aquatic life. There is an urgent need to propose sustainable and cost-effective engineering technologies to remove excess phosphate and nitrate ions in wastewater streams effectively before discharging them to the receiving bodies or their reuse
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