Remediation of Aqueous Phosphate Agricultural Runoff Using Slag and Al/Mg Modified Biochar

Abstract

Slag and Al/Mg oxide modified Douglas fir biochar (AMOB) were compared for their phosphate adsorbing abilities for use individually or in combination for simulated agriculture run-off remediation in wetlands. Aqueous batch and column sorption experiments were performed for both low-cost materials. AMOB was prepared in bulk using a novel green method. Material analyses included XRD, elemental analysis, SEM, EDX, and BET. Biochar and slag have different phosphate removal mechanisms. In short residence times (≤2 h), adsorption phenomena dominate for both adsorbents. Surface area likely plays a role in adsorption performance; slag was measured to be 4.1 m2/g while biochar’s surface area was 364.1 m2/g. In longer residence times (>2 h), the slow leaching of metals (Ca, Al, and Mg) from slag continue to remove phosphate through the precipitation of metal phosphates. In 24 h, slag removed more free phosphate from the solution than AMOB. Preliminary fixed bed column adsorption of slag or AMOB alone and in tandem was performed adopting a scaled-up model that can be used to remediate agricultural runoff with high phosphate content. Additionally, a desorption study was performed to analyze the efficiency of material regeneration. While AMOB does not release any adsorbed phosphates, slag slowly releases 5.7% adsorbed phosphate over seven days.

Removal of Phosphorus from Domestic Sewage in Rural Areas Using Oyster Shell-Modified Agricultural Waste–Rice Husk Biochar

“…cium active components contribute to the adsorption of P onto the Ca-BC (2:1)-T900 by strong chemical interaction mechanisms, resulting in the high adsorption capacity of the Ca-BC (2:1)-T900 for P over a wide pH range (3)(4)(5)(6)(7)(8)(9)(10)(11).…”

“…Different biological, chemical, and physical techniques have been created and widely applied in previous studies to manage and treat the phosphorus (P) present in wastewater [4,5]. Among those methods, the adsorption method is the most attractive since it is economically feasible and simple in real application; in addition, the nutrient-loaded adsorbents can be further utilized as soil conditioners and fertilizers [6].…”

“…This is due to the fact that the presence of H + can hinder the complexion of P with Ca[18,19], indicating that the presence of H + most likely pacifies the active binding sites for P[18,28]. In addition, calcium active components contribute to the adsorption of P onto the Ca-BC (2:1)-T900 by strong chemical interaction mechanisms, resulting in the high adsorption capacity of the Ca-BC (2:1)-T900 for P over a wide pH range(3)(4)(5)(6)(7)(8)(9)(10)(11).…”