The Hong Kong Polytechnic University Phosphorus Recovery from Incinerated Sewage Sludge Ash (ISSA) and Turn into Phosphate Fertilizer Student :Le FANG Supervisor: C. S. POON ----June. 2018
Contents • Background and motivation • Clarification of research key points • Current results • Conclusions
Contents • Background and motivation • Clarification of research key points • Current results • Conclusion
Incineration in Hong Kong - T-Park 1200 tons sewage sludge originated from 11 wastewater T ‐ Park treatment plants in Hong Kong. Turn waste into energy. Thermal energy in incineration process was collected and transferred into electricity. Volume reduction by 90%. Main Sewage Treatment Works Locations Decreased burden for landfill capacity. 2 s under 850 C. Least formation of harmful organic pollutant. Incinerated sewage ash which was present disposal by landfill.
Incineration in Hong Kong - T-Park 1200 tons sewage sludge T ‐ Park originated from 11 wastewater treatment plants in Hong Kong. Turn waste into energy. Thermal energy in incineration process was collected and transferred into electricity. Volume reduction by 90%. Decreased burden on landfill capacity. 2 s under 850 C. Minimal formation of harmful organic ISSA pollutant. Incinerated sewage ash currently disposal of at landfill.
Contents • Background and motivation • Clarification of research key points • Current results • On-going and plan to do…
Research structure Characteristics: pH, specific gravity, LOI, Methods Results XRF, XRD, SEM, BET High Fe ISSA Physical/chemic HK ISSA Potential P al characteristics resource sink Leaching by A two step P leaching three kind of leaching agents process Absorption. Final recovery Fractional Purification ratio precipitation. Three kind Constituents P fertilizer fertilizers. analysis. Simplify the Design of Cost of the Potential leaching reaction vessel application application area process process Practical applications of P fertilizer
Contents • Background and motivation • Clarification of research key points HK ISSA • Current results P leaching • Conclusion Purification
Characteristics of Hong Kong ISSA 6 5 Hong US ISSA(Donatello Items Kong and Cheeseman 4 ISSA 2013) Volume (%) 3 Specific gravity 2.49 2.14-2.9 2 pH 8.45 7.6-8.8 1 Mean particle Physical 56.0 51.2-108.8 0 Suitable substitute size ( μ m) properties 0.01 0.1 1 10 100 1000 BET surface for phosphorite 3.42 6.4-23.8 % ( μ m) area (m 2 /g) HK ISSA: Loss on ignition deposit. 0.99 0.9-2.1 (%) 3000 A:A northite A Q F:Feldspar Na 2 O 2.21 0.01-6.8 2500 H:H em atite Density (Counts) Q:Q uartz Fine ash. MgO 1.54 0.02-23.4 2000 W :W hitlockite 1500 F A Al 2 O 3 11.56 4.4-34.2 Q H H Q W 1000 H SiO 2 33.35 14.4-65.0 F Q Q F Nearly no organic matter. F W 500 P 2 O 5 9.16 0.3-26.7 0 Cl 0.28 — 0 20 40 60 80 D egree (2Theta) High Fe ISSA. SO 3 4.04 0.01-12.4 Chemical composition K 2 O 3.50 0.1-3.1 (%) CaO 9.54 1.1-40.1 Contain significant P but co- TiO 2 0.55 0.3-1.9 Cr 2 O 3 0.09 — exist with Fe, Al, Ca. MnO 0.12 — Fe 2 O 3 22.60 2.1-30 — CuO 0.18 ZnO 0.69 —
P leaching by three kind of extraction agents Significant P was leached out by acids. Limited P leaching.
Co-leaching of metal(loid)s Inorganic Inorganic Organic Organic Chelatin Chelatin acid acid acid g agents acid g agents
Co-leaching of metal(loid)s Inorganic Inorganic Organic Organic Chelatin Chelatin acid acid acid g agents acid g agents Metal(loid)s were leached out with limited P leaching .
Two-step P extraction • EDTA Pretreatment Metal(loid)s were leached out with limited P leaching. Optimized pretreatment conditions: 3 hour reaction at a pH of 1.3, at a liquid-to-solid ratio of 20:1 and concentration of 0.02 mol/L. • Sulphuric acid P extraction High efficiency in P extraction with relatively low metal(loid)s co- dissolution. Optimized P extraction condition (94%) ： 2 hour reaction with 0.2 mol/L at a liquid to solid ratio of 20:1.
Two-step leaching process with factional precipitation 1. Two-step leaching decreased concentration of metal(loid)s, such as Cr (by 92%), Zn (by 58%), Mn (by 50%), Mg (by 49%), Cu (by 49%), Al (by 37%), Fe (by 23%), etc. 2. Subsequent pH adjusting by Ca(OH) 2 would induce formation of Ca-P. Ca(OH) 2 Two-step 2-extract extraction pH=4 ISSA 2-Ca Filtrated and dried P-extract NaOH pH=4 P-free 2-Na 1 st step: EDTA pre-treatment residue 2 nd step: sulphuric acid extraction Ca(OH) 2 1-extract Single-step extraction 1-Ca ISSA P-extract NaOH pH=4 P-free 1-Na residue sulphuric acid extraction
Purification of P-extract from two-step methods (to remove Al, Fe, Ca, Zn, etc.) Activated Low absorption carbon efficiency in acids. 732 High absorption cationic efficiency in acids. resin
Purification-absorption 24 Mg Al Ca Fe Zn Extraction mass (mg/g) MAC can remove metal(loid)s 16 marginally. 8 0.27 Sb Se Ni As Cd Cr Mn Pb Cu 0 MAC 732 resin leachate Extraction mass(mg/g) 0.18 0.035 0.030 Obvious reduction of 0.025 major metal(loid)s. 0.020 0.015 0.010 0.005 0.000 leachate MAC 732 resin
Modified biochar for phosphorus absorption 1. Soaking with Mg-Ps Biochar MgCl 2 solution Peanut shell (PS) Mg-Sc Biochar Pyrolysis v Ca-Ps Biochar 2. Soaking with CaCl 2 solution Ca-Sc Biochar Sugarcane bagasse (Sc) Biochar laden with phosphorus – a kind of fertilizer
Optimal biochar for phosphorus absorption 100 90 Phosphorus absorption efficiency(%) 80 70 60 50 40 30 20 10 0 Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700 Biochars Pristine biochars have low phosphorus removal capacity.
Optimal biochar for phosphorus absorption 100 90 Phosphorus absorption efficiency(%) 80 70 60 50 40 30 20 10 0 Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700 Biochars Pretreating of Ps & Sc with CaCl 2 cannot significantly improve phosphorus removal capacity.
Optimal biochar for phosphorus absorption 100 90 Phosphorus absorption efficiency(%) 80 70 60 50 40 30 20 10 0 Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700 Biochars Pretreatment of Ps & Sc by MgCl 2 can produce biochars with high phosphorus removal capacity.
Optimal pyrolysis temperature on phosphorus absorption 100 90 Phosphorus absorption efficiency(%) 80 70 60 50 40 30 20 10 0 Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700 Biochars Biomass pyrolysis at 700 o C produced the highest P removal biochar.
Biochars laden with phosphorus Spectrum 1 PsM700 Spectrum 1 Before absorption After absorption Spectrum 2 ScM700 Spectrum 2
Contents • Background and motivation • Clarification of research key points • Current results • Conclusions
Conclusions • Two-step leaching method can not only decrease metal(loid)s in extraction but also increase phosphorus-purity for the subsequent purification step. • Precipitation of leachate from the two-step method by Ca(OH) 2 pH adjustment induces formation of Ca-P. • 732 cationic resin is efficient in removing macro-metalloids like Al, Mg, Zn, Fe and Cu. The purified leachate can be used for liquid phosphorus fertilizer. • Both biomass of Ps and Sc have high phosphorus removal capacity after pretreatment by MgCl 2 and pyrolysis at 700 o C. And ScM700 has advantages of higher phosphorus adsorption capacity, less adsorbed metal(loid)s and lower working pH over PsM700.
Thank you!
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