Question

7. The behaviour of lead in soil/water systems has been described in terms of Langmuir adsorption. From laboratory experiments using 'pure solids, the following values for Langmuir parameters have been estimated For clay b = 3200 L mol- Com = 4x10-4 mol g For organic matter b = 10 000 L mol-' Csm = 4x10-4 mol g -7 (a) Use these values to calculate the concentration (in mg L or ppb) of water-soluble lead in equilibrium with clay containing 5 ppm adsorbed lead, and with organic matter also containing 5 ppm adsorbed lead. Both soil concentrations are those found at equilibrium.

Answer 1

Sol Given data for clay b=3200 L mor = 32001 - 15.444 L = 15.444 X 10 207.29 cm = 4 Xeomol = 207,29/mor me 4x10molls - 8.288 malg 80, q= 5ppm = 5x1o6 mg = 5x19 mele q=wmax Cb cfl + bcf) emax = maxi'um uptake of absorjate z cm (molly q- amount of absorbate uptake b= coefficient of affinity between absorbent and absorbate. of=final metal Concentration (male) a=&max (beboll the f) (10 mg = 5.295 mg x (15-44 xt6 3 Ming xci) X (1+ 15-444x153 0.603x169 = (15.444x 16 mg 6%) ites.uuukio34 x 6] 0.6038109 +9.317x10 x 60C +9.317XIO lng (15.444x1, 1,49 loungty

0- 403 vi61 — (15.4ч хліб'юк) ng is very small to ignored] с = 0-603x61 = 0.0390 x64 WS | 1f444xus 3 с му с : 3.9 x to me for organic matter 4 – ау (5 | 1+6+) 9 = 5x156mg = 6х6 1 1 cm= max = 4x154, m. = 4х16° mo ( x 201, 24tno | x 1000 cm3 (я = 0.0Чеѕ ЧЈms = 82,88 maig Бs tboo Ч mot = (ороос 201,2 кі000 m/s q=&max (beliebt) Ухліб 1/ka se 2 o-че< me ( ( (tto 04e sym, xce) О. осоз хіб 1 20.04€ 3*+ (1+0.04€ е с o-06 3х16+0. 00241 161 xc - - 0.04% 1 . О-осо3x16° = 0.04% 3 m, xes &= 1.298x109 mg чеѕ », « ) — . .