Phosphorus Release and Adsorption Properties of Polyurethane–Biochar Crosslinked Material as a Filter Additive in Bioretention Systems

Abstract

Bioretention systems are frequently employed in stormwater treatment to reduce phosphorus pollution and prevent eutrophication. To enhance their efficiency, filter additives are required but the currently used traditional materials cannot meet the primary requirements of excellent hydraulic properties as well as outstanding release and adsorption capacities at the same time. In this research, a polyurethane-biochar crosslinked material was produced by mixing the hardwood biochar (HB) with polyurethane to improve the performance of traditional filter additives. Through basic parameter tests, the saturated water content of polyurethane-biochar crosslinked material (PCB) was doubled and the permeability coefficient of PCB increased by two orders of magnitude. Due to the polyurethane, the leaching speed of phosphorus slowed down in the batching experiments and fewer metal cations leached. Moreover, PCB could adsorb 93–206 mg/kg PO43− at a typical PO43− concentration in stormwater runoff, 1.32–1.58 times more than HB, during isothermal adsorption experiments. In the simulating column experiments, weaker hydropower reduced the PO43− leaching quantities of PCB and had a stable removal rate of 93.84% in phosphate treatment. This study demonstrates the potential use of PCB as a filter additive in a bioretention system to achieve hydraulic goals and improve phosphate adsorption capacities.

Ammonium Release and Adsorption Characters of Polyurethane–Biochar Crosslinked Material as an Additive Filler in Stormwater Treatment

“…Polyurethane–biochar crosslinked material (PCB) was synthesized with a simple one-shoot method, where glycol, deionized water and hardwood biochar were mixed with methylene diphenyl diisocyanate (MDI). For the formulations and detailed polymerization process of PCB, readers can refer to the published article [ 26 ].…”

“…The physicochemical characterizations indicators of additive fillers include natural bulk density (ρ), the saturated moisture content (ω sat ), particle size, specific gravity, pore ratio (e), permeability coefficient (K), specific surface area (BET), pH, cation exchange capacity (CEC), total nitrogen content (TN), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The methods of testing the physicochemical characterizations of additive fillers were consistent with the published article [26]. Additionally, TN of additive fillers was measured by combustion using a Multi N/C2100 Elemental Analyzer (Jena, Germany).…”

“…As for nitrogen leaching, the releasing quantities and rates become slower when fertilizers are coated by the polyurethane [ 25 ]. In addition, our recently published article has also proved that polyurethane–biochar crosslinked material (PCB) is a new polymer material which has high water retention capacity, low phosphorus leaching quantities, as well as high phosphorus adsorption capacity [ 26 ]. The network of polyurethane in PCB restrained the release of phosphorus from interpenetrated biochar, and promoted the phosphate removal rate form the runoff.…”

Char Valorization into Sustainable and Performant Polyurethane Insulating Panels

“…For instance, char addition might contribute to energy reduction related to the production process of construction materials, carbon sequestration, reduction of the firing temperature, reduction of raw materials exploitation, and properties optimization. [2][3][4][5][6] Applications into polyurethane products provide interesting filtering and antipollutant properties, [7][8][9] although no further studies have focused on the mechanical, thermal, and electrical properties of polyurethanes for insulating panels real applications. In this work, the char deriving from the gasification of Secchia River Biomass (Emilia Romagna, Northern Italy) was considered as a viable secondary raw material for insulating construction materials and as a possible solution toward economic and environmental sustainability of the river maintenance process.…”

Rigid Polyurethane Foams Modified with Biochar

“…So far, examples of applications of BioC in polyurethane-based systems have been described very rarely. In the research conducted by Meng et al, BioC-modified porous polyurethanes were used as the filter components in a bioretention system [ 17 ].…”