Search

• The P in the sludge was mainly NAIP, OrgP and AP were less abundant. • At 700–1100 ℃, the content of AP in incineration ash was high. • More HCl was released for sludge incinerated at 700–1100 ℃. • Main release was at 700–1100 ℃ for InorgF and at 600–800 ℃ for OrgF. Sludge is often incinerated to achieve complete harmlessness and maximum capacity reduction, but the utilization of P (phosphorus) and the environmental pollution of F (fluorine) and Cl (chlorine) released from sludge incineration are usually ignored. In this paper, a series of experiments were employed to inquire into the conversion of various forms of P and the release of various forms of F and Cl after sludge incineration at different temperatures; the agriculture application prospect of P in sludge incineration ash and the environmental pollution caused by the release of F and Cl were discussed. The results show that P in sludge mainly exists as NAIP (non-apatite inorganic P) which biological effect was small. In the process of sludge incineration, InorgP (inorganic P) began to volatilize at 900 ℃, and the remaining P in sludge ash was 30.96 % at 1100 ℃. The forms of P in sludge incinerated at different temperatures varied considerably: a small amount of OrgP (organic P) in the sludge was converted into InorgP at 400 ℃; with the increase of incineration temperature, AP (apatite P) increased gradually, with 3.00 × 103–7.98 × 103 g/t in sludge ash at 700–1100 ℃. At 900 ℃, the content of AP in incineration ash was the highest, accounting for 58.98 % of Total P, which was the most suitable for slow-release phosphate fertilizer. At 600–1100 ℃, more Cl release, with a release rate of 50.61–92.70 %, among which the Cl for HCl (Cl HCl) was 1.64 × 103–1.95 × 103 g/t at 700–1100 ℃. The F release rate was 1.52–37.39 %, among which the InorgF (inorganic F: mainly refers to F in HF and SiF 4) was 1.13–27.91 g/t at 300–1100 ℃, the release amount of OrgF (organic F) was 1.59–1.86 g/t at 600–800 ℃. It can be seen that after incineration above 700 ℃, the sludge incineration ash may be used as a slow-release phosphate fertilizer, the release of Cl has greater environmental pollution and instrument corrosion than that of F, and the exhaust gas from sludge incineration cannot be discharged directly into the atmosphere. [ABSTRACT FROM AUTHOR]

Fluorine and chlorine are important tracers for geochemical and environmental studies. In this study, a rapid alkaline digestion (NaOH) method for the simultaneous determination of fluorine and chlorine in marine and stream sediment reference samples using ion chromatography is developed. The proposed method suppresses the volatilization loss of fluorine and chlorine and decreases the matrix effects. The results are in good agreement with fluorine ~100%, chlorine ranging from 90 to 95% of the expected concentrations. The detection limits of this method were 0.05 μg/g for fluorine and 0.10 μg/g for chlorine. This method is simple, economical, precise and accurate, which shows great potential for the rapid simultaneous determination of fluorine and chlorine in large batches of geological and environmental samples commonly analyzed for environmental geochemistry studies.

Fluorine and chlorine are important tracers for geochemical and environmental studies. In this study, a rapid alkaline digestion (NaOH) method for the simultaneous determination of fluorine and chlorine in marine and stream sediment reference samples using ion chromatography is developed. The proposed method suppresses the volatilization loss of fluorine and chlorine and decreases the matrix effects. The results are in good agreement with fluorine ~100%, chlorine ranging from 90 to 95% of the expected concentrations. The detection limits of this method were 0.05 μg/g for fluorine and 0.10 μg/g for chlorine. This method is simple, economical, precise and accurate, which shows great potential for the rapid simultaneous determination of fluorine and chlorine in large batches of geological and environmental samples commonly analyzed for environmental geochemistry studies. [ABSTRACT FROM AUTHOR]

A series of experiments for calcination and subsequent digestion to increase the grade of phosphate rock were performed. Fluorine and chlorine released by calcination and digestion were investigated. The forms of both elements were studied by sequential chemical extraction. The grades of raw and calcined phosphate rocks, and their phosphorus concentrates were confirmed according to the value of P 2 O 5 %. The results showed that fluorine and chlorine in phosphate rock mainly existed in carbonate-bound and residual forms. The grade of phosphate rock can be well increased by calcination and subsequent digestion. By digestion at the optimal condition of 2.5:1 for liquid-solid ratio, 60 °C for digestion temperature and 50 min for digestion time, the phosphorus concentrates digested from the calcined phosphate rock of 1000 °C reached the highest grade (P 2 O 5 % = 33.24%). By calcination, the released fluorine was mainly HF at a low temperature and SiF 4 at a high temperature, with fluorine release amount of 1.61 × 104–3.82 × 104 g/t at 900–1100 °C. Cl 2 , HCl and Cl− were mainly released at 200–500 °C, less than 800 °C and more than 800 °C, which release amount were 9.40 × 10–2.54 × 102 g/t, 2.10 × 102–1.53 × 104 g/t and 2.24 × 102–5.61 × 102 g/t, respectively. By digestion with water for the calcined phosphate rock of 900–1100 °C, the concentrations of fluorine and chlorine in effluent were respectively 77.2–160 mg/L and 7.99–19.6 mg/L. It can be concluded that fluorine and chlorine released by calcination for phosphate rock contribute greatly to atmospheric acid rain and equipment corrosion; by digestion, the discharge of fluorine seriously exceeds the standard and may cause greater pollution to the water body. Image 1 • Fluorine and chlorine mainly exist in carbonate-bound and residual form. • Calcination and digestion can increase the grade of phosphate rock. • Cl 2 , HCl and Cl− were respectively released at low, medium-low and high temperature. • Fluorine and chlorine released by calcination contribute greatly to the environment. • By digestion, the released fluorine seriously exceeds the standard. By calcination and digestion, the grade of phosphate rock is increased greatly, and more fluorine and chlorine are released. [ABSTRACT FROM AUTHOR]