A comparative study on phosphate removal from water using Phragmites australis biochars loaded with different metal oxides

Abstract

Metal oxide-loaded biochars are a promising material to remove phosphate from polluted water to ultra-low concentrations. To facilitate preparing the metal oxide-loaded biochar with the best phosphate adsorption performance, five biochars loaded with Al, Ca, Fe, La and Mg oxides, respectively (Al-BC, Ca-BC, Fe-BC, La-BC and Mg-BC) were produced using Phragmites australis pretreated with 0.1 mol AlCl 3 , CaCl 2 , FeCl 3 , LaCl 3 and MgCl 2 , respectively, characterized, and phosphate adsorption kinetics and isotherms of the biochars were determined. The maximum phosphate adsorption capacities ( Q m ) of the biochars ranked as Al-BC (219.87 mg g −1 ) > Mg-BC (112.45 mg g −1 ) > Ca-BC (81.46 mg g −1 ) > Fe-BC (46.61 mg g −1 ) > La-BC (38.93 mg g −1 ). The time to reach the adsorption equilibrium ranked as La-BC (1 h) < Ca-BC (12 h) < Mg-BC (24 h) = Fe-BC (24 h) <Al-BC (greater than 72 h). Q m of Ca-BC, Fe-BC, La-BC and Mg-BC depend on the molar content of metals in the biochars. The small phosphate adsorption rate of Al-BC is due to the slow intra-particle diffusion of phosphate attributed to the undeveloped porosity and dispersed distribution of AlOOH crystals on the Al-BC surface. Mg-BC is suggested for phosphate removal from water considering adsorption rate and capacity. Al-BC is applicable when a long contact time is allowed, e.g. as a capping material to immobilize phosphate in lake sediments.

Biochar-Based Adsorbents for Pesticides, Drugs, Phosphorus, and Heavy Metal Removal from Polluted Water

“…We can conclude that there is increasing evidence for the use of biochar as an attractive adsorbent material for the removal of several chemical and biological contaminants arising from its large surface area, recalcitrance, porosity, and presence of various surface functionalities, making it an efficient and cost-effective sorbent rooted in waste valorization and sustainability [51][52][53]. Also, biochar is largely used in soil remediation and amendment and can be designed to work as a slow-release fertilizer to improve soil quality and productivity with environmental and economic benefits [54][55][56][57].…”

The Removal of Phosphorus from Wastewater Using a Sewage Sludge Biochar: A Column Study

“…Carbonaceous materials like biochar have been employed as effective solid sorbents for soil amendment, phosphorus removal, and carbon capture. The biomass feedstock for producing the biochars can come from spruce [18], reeds [19], sheep manure [20], dairy cow slurry [21], date seed biochar [22], and sewage sludge [23]. Due to its sustainability and low-cost benefits for treating wastewater containing heavy metals, sludge biochar has recently attracted much attention [24].…”