1. Calculate the pH of water in a cloud that has equilibrated with 1.0 ppm by volume SO2.
2. The raw water supply for a community contains 18 mg/L total particulate matter and is to be treated by addition of 60 mg alum (Al2(SO4)3.18 H2O) per liter of water treated (Hint: You can use Visual Minteq for part b and c).
(a) For a total flow of 8000 m3/d, compute the daily alum requirement and the concentration of solids in the water following alum addition, assuming the alum all precipitates as Al(OH)3(s).
(b) The water is initially at pH 7.5 and has ALK 7 40 mg/L as CaCO3. It is desired to maintain solution pH at 6.5 or higher. Will the pH be in the acceptable range after the chemical additions and Al(OH)3(s) precipitation?
(c) What will the pH be if the treated solution is bubbled with air, so that it reaches equilibrium with atmospheric CO2?
3. Adsorption of benzene onto activated carbon has been reported to obey the following Freundlich isotherm equation, where c is in mg/L and q is in mg/g: 0.533 q benz = 50.1 Cbenz a) Demonstrate how do the units work out for the equation above? In other words, what's the unit for the Freundlich constant K=50.1? b) A solution at 25°C containing 0.50 mg/L benzene is to be treated in a batch process to reduce the concentration to less than 0.01 mg/L. Compute the required activated carbon dose in mg/L. Specify the units for all the terms.
4. Stillings et al. (1998) report the following data for adsorption of oxalate species onto a natural aluminosilicate mineral. The data were collected in solutions at pH 3-5, but the authors found that the total adsorption of oxalate was independent of pH in this range.
(a) Estimate best-fit parameters to model the data according to the Langmuir and Freundlich isotherms.
(b) Use the isotherms derived in part (a) to estimate the adsorption density at an equilibrium dissolved oxalate concentration of 10 mmol/L. Which estimate would you use if you needed to predict qox for those conditions?
(OX)diss,eq (mmollL) ClOx (Rmollm2) 0.00 0.00 0.65 8.03 0.94 6.50 1.00 2.60 1.54 16.74
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,*4
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1.65 1.93' 3.45 3.49 3.54 6.50 6.53 6.81
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11.52 10.93 16.84 18.17 18.07 23.69 23.38 18.20
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5. One gram of solid Cd(OH)2(s) is dispersed in a solution at pH 9.0 containing 1.0 mg/L Cd24.
Do you expect some solid to dissolve, some dissolved Cd to precipitate, or no change in the solution composition?