Adsorption Behaviors and Removal Efficiencies of Inorganic, Polymeric and Organic Phosphates from Aqueous Solution on Biochar Derived from Sewage Sludge of Chemically Enhanced Primary Treatment Process

Guoren Xu,Linyu Deng,Zhao Zhang

doi:10.3390/w10070869

Abstract

Adsorption behaviors and removal efficiencies of different phosphorus species on sewage sludge-based biochar (SBB) were investigated, with powder activated carbon (PAC) as a comparison. The adsorption efficiencies of potassium dihydrogen phosphate, sodium tripolyphosphate and sodium glycerol-phosphate on SBB are 81.91%–92.86%, 66.02%–90.66% and 25.48%–38.94%, when the initial pH values of phosphate solutions are 3–10, 4–10 and 3–10, respectively. The maximal adsorption capacities of phosphates on SBB are 2.1–5.3 times those of PAC. X-ray photoelectron spectroscopy analysis indicates that ligand-exchange mechanism and Lewis acid-base interactions occur between hydrolysates of surface-Fe2+/surface-Fe3+ and phosphates, and the precipitates of phosphates accumulate on the surface of SBB and separate from the aqueous solution. These results demonstrate that SBB is an effective adsorbent for phosphorus removal and recovery in wastewater, and it also has the potential to reduce phosphorus leaching loss in the soil when applied in soil amendment.

Highlights

Phosphorus is a limiting nutrient leading to eutrophication, and it is a scarce nutrient, as mineable deposits of phosphate rock are limited [1]
Phosphorus in sewage, fertilizers, and soil is present in the forms of organic phosphate, inorganic phosphate and polyphosphate, and organic phosphorus is more mobile than recalcitrant forms, comprising 22%–46% of total phosphorus
Organic phosphate is often overlooked in phosphorus removal and recovery [4]

Summary

Introduction

Phosphorus is a limiting nutrient leading to eutrophication, and it is a scarce nutrient, as mineable deposits of phosphate rock are limited [1]. Sewage-effluent phosphorus is the main point-source of excess phosphorus discharged to waters, and phosphorus in runoff from agricultural land is a major component of nonpoint-source pollution [2,3]. Enhancing phosphorus removal and recovery from sewage and reducing phosphorus leaching loss in soil have significant meaning to address eutrophication and phosphorus crisis. Phosphorus in sewage, fertilizers, and soil is present in the forms of organic phosphate, inorganic phosphate (orthophosphate) and polyphosphate, and organic phosphorus is more mobile than recalcitrant forms, comprising 22%–46% of total phosphorus. The most common approaches of phosphorus-removal and recovery technologies are metal precipitation, ion exchange, struvite crystallization, and biological uptake from sewage, with the final product as phosphate salts or sludge [5,6]

Methods

Results

Conclusion