Phosphate removal from aqueous solutions using raw and activated red mud and fly ash

Abstract

The effect of acidification and heat treatment of raw red mud (RM) and fly ash (FA) on the sorption of phosphate was studied in parallel experiments. The result shows that a higher efficiency of phosphate removal was acquired by the activated samples than by the raw ones. The sample prepared by using the RM stirred with 0.25 M HCl for 2 h (RM0.25), as well as another sample prepared by heating the RM at 700• C for 2 h (RM700), registered the maximum removal of phosphate (99% removal of phosphate). This occurred when they were used in the phosphate sorption studies conducted at pH 7.0 and 25• C with the initial PO 4 3− concentration of 155 mg P/l. The FA samples treated in the same way described above can achieve 7.0 and 8.2 mg P/l phosphate removal for FA0.25 and FA700 respectively, corresponding to 45.2% and 52.9% removal. The activated materials performed higher phosphate removal over broader pH range compared with the raw ones. The influences of various factors, such as initial pH and initial phosphate concentration on the sorption capacity were also studied in batch equilibration technique. Solution pH significantly influenced the sorption. Each sample achieved the maximal removal of phosphate at pH 7.0. The amount of phosphate removal increased with the solute concentration. The Freundlich and Langmuir models were used to simulate the sorption equilibrium. The results indicate that the Langmuir model has a better correlation with the experimental data than the Freundlich model.

Comparisons Study of Phosphate Removal in Unaerated and Aerated High Calcium Steel Slag Filter System of Different pH Feed

“…The utilization of low-cost and easily available materials as the filter media has been widely demonstrated by previous studies for their reliability and contribution in the removal of phosphate including fly ash [4], limestone [5], iron oxide tailings [6], blast furnace slag [7], basic oxygen furnace slag and electric arc furnace slag [8].…”

Phosphorus Adsorption Capacity Evaluation for the Substrates Used in Constructed Wetland Systems: a Comparative Study

“…Previous results have shown that substrate adsorption plays the most important role in P immobilization [4][5][6][7][8]. Therefore, cheap and effective P adsorbents are highly desirable [9][10][11].The most commonly used substrates in CWs are quartz sands [12], activated carbon (AC) [12][13], zeolite [14], ceramic [15], and furnace slag [16][17], and prior research has shown that the removal of P by these substrates mainly occurs though physical adsorption, chemical precipitation, and ion exchange [10][11]. However, P sorption properties of the substrates have not been systematically estimated, which resulted in many defective packing layer designs for CWs [3,11].…”

Phosphorus removal from domestic sewage by adsorption combined photocatalytic reduction with red mud

“…Previous studies have shown that the adsorption capacity of the phosphorus exists in many lowcost sorbents, such as fly ash [13], bentonite, natural zeolite, alum sludge [14], red mud [15][16][17][18], and other waste materials [19]. Red mud (RM) is a waste residue formed after the caustic digestion of bauxite during the production of alumina.…”

“…The visible light from the high-pressure mercury lamp (125 W) irradiated perpendicularly to the solution and the distance between the lamp and the liquid level was 30 cm. At given irradiation time intervals (5,15,30,45,60, and 90 min), liquid samples were taken from the suspension and settled for 4 h, and then, the phosphorus in the supernatant was measured. …”