The influence of defoamer on removal of PAHs in soil washing

Figures & data

Table 1. Properties of the soil studied

TOC (%)	0.65
Moisture content (%)	0.78
pH (H2O)	8.4
CEC (cmol kg^−1)	8.42
Porosity (%)	40.5
Soil density (g/cm^3)	2.73
Particle size distribution (%)
<50 µm	4.33
50–75 µm	8.95
75–125 µm	43.22
125–250 µm	18.49
250–500 µm	12.72
500–2000 µm	12.29

Figure 1. Stirring reactor of soil washing. 1, Grid agitator; 2, agitator tank; 3, adjusting cell: power key, speed adjustment cell, rotate-direction controlling cell; 4, rotating motor; 5, stainless steel support.

Figure 2. The change of the foam height with time in different concentrations of kieselguhr.

Figure 3. The change of the foam height with time in different concentrations of dodecanol.

Figure 4. The change of the foam height with time in different concentrations of PDMS.

Table 2. Foam properties with different concentrations of additives

Additive type	Kieselguhr
Concentration (%)		0	0.01	0.02	0.03	0.04	0.05	0.07	0.1
Initial foam height (cm)		115	130	127	110	147	148	158	155
Half-life period (sec)		3794	210	150	428	754	823	824	781
Additive type	Dodecanol
Concentration (%)		0	0.01	0.02	0.03	0.04	0.05	0.07	0.1
Initial foam height (cm)		115	96	101	85	86	92	90	81
Half-life period (sec)		3794	441	243	267	219	166	114	107
Additive type	PDMS
Concentration (%)		0	0.01	0.02	0.03	0.04	0.05	0.07	0.1
Initial foam height (cm)		115	106	72.5	57.5	49.5	45	40	38
Half-life period (sec)		3794	120	103	41	29	28	16	15

Figure 5. The defoaming performance of PDMS oil during the soil washing process: (a) the foam of slurry without PDMS oil at the beginning of soil washing (no stirring), (b) the foam of slurry without PDMS oil during the soil washing (washing time = 30 min), (c) no foam of slurry with PDMS oil at the beginning of soil washing (no stirring), and (d) no foam of slurry with PDMS oil during the soil washing (washing time = 30 min).

Figure 6. The surface tension with the addition of PDMS.

Figure 7. The solubilizing ratio of Σ PAHs with the different addition concentrations of PDMS oil.

Figure 8. Effect of PDMS oil on ΣPAHs removal.