Initial Step – Using MINTEQ, determine the composition of the river water by specifying the given ALK and pH and running the program to find that TOTCO3 and TOTH from the output under the “EQUILIBRATED MASS DISTRIBUTION” option. To do so:1. Open MINTEQ2. Set pH at fixed at and enter 7.53. Go to the top bar and select “PARAMETERS” and then “SPECIFY ALKALINITY”. Here, select the units (meq/L) and enter the value given in the problem statement. Note the difference in units though! Finally, click OK4. Run MINTEQ and in the output window, click on “EQUILIBRATED MASS DISTRIBUTION” AND WRITE DOWN THE THE TOTAL DISSOLVED CONCENTRATIONS OFCO3-2 AND H+. These are TOTCO3 and TOTH. Second stepUse Visual MINTEQ again, and representing the determined river chemical composition as the ‘baseline’ solution, explore various additions of the wastewater to the river water to identify the mixing ratio that causes the pH to be 6.0. Use Visual MINTEQ titration tool. Steps are as follows: Start a new MINTEQ solution, and make sure to delete the alkalinity value entered earlier, as well as the pH of 7.5Now, set up the pH to calculated based on mass balance In the component window, enter the concentrations of TOTCO3 (as CO3-2) and TOTH (as H+) determined above. That is: Next, go to “Multi-Problem sweep” on the top bar of MINTEQ Select titration / mixing with a titrant with defined composition and then set up the state of titration steps to some number (e.g. 41)Going down the screen, under component/species, select H+ For the type (which type?) – select activity Then click ADD. Go back on the top section of the screen, and on the right of the “titration/mixing” option selected earlier, click on “Go to Titration Manager” On this screen, do the following Volume (mL) of solution to titrate (e.g. 1000)Volume (mL) of titrant (e.g. 0.2)Concentration unit of titrant: mol/L Check the box for titration not to start till second addition Define titrant composition by entering the following: Enter molar conc. (e.g. mol/L), and then the component (e.g. H+) and click on save and next. Enter the second component (e.g. SO4-2), repeat the steps above as for H+, but selecting sulfate as component. For this problem, you will stop here. Click on “Save and go back to multi/sweep menu” Then click on “Save and back” Now back to the main menu – RUN MINTEQ From the output, select “SELECTED SWEEP RESULTS” and in the table, the titration number corresponding to pH 6.0 or the closest to 6.0, if the exact pH is not shown Determine the volume of titrant added to obtain the pH of 6Determine the dilution factorPROBLEM-2The dose of OH- that must be added to bring the pH to 5.5 can be equated with the decline in TOTH between the initial condition and the neutralized solution. Knowing TOTSO4, TOT Fe, and pH, we can specify the inputs Next, use the “Solid phases and excluded species” menu to exclude consideration of the species we wish to ignore based on recommendations in the problem MINTEQ. The results should give something like TOTH = 0.529M at pH 0.8 and TOTH = -198M at pH 5.5The difference between these two TOTH values corresponds to the molar concentration of OH- to be added. Since 1 mole of lime (Ca(OH)2) contributes 2 moles of OH-, the required lime dose to supply the needed [OH-] would be equivalent to half of the calculated concentration in step-X The titration curve can be generated using Visual MINTEQ by instructing the program to compute the pH as a function of lime dose, resulting in the following curve Inputs: (SO4-2 = 0.4M, Fe+2 = 0.1M, Ca+2 = 0.Excluded species: CaSO4 and FeSO4Ionic strength fixed at 0.1M
PRINCIPLES OF WATER CHEMISTRY HOMEWORK
- This is a MINTEQ problem, and your solution should be presented as a typed report including all relevant screenshots
- Handwritten documents will not be graded
- SUBMISSION should be THROUGH CANVAS ONLY. Email submissions are not be accepted
Problem-1 (50 points)
A waste solution containing 0.1 M sulfuric acid is to be discharged into a river, which has near neutral water with a pH of 7.5 and a carbonate alkalinity of 2×103 equiv/L. If we consider the mixing process resulting from this discharge to be a titration of the river water with the acidic wastewater:
- Using MINTEQ, determine to what extent the wastewater must be diluted (i.e., what volume of river water must be combined with a unit volume of the wastewater) to assure that the pH of the resulting mixture does not drop below 6.0?
Problem-2 (50 points)
An industrial wastewater from a “pickling” process contains 0.4 M TOTSO4 and 0.1 M TOTFe at pH 0.8. (Pickling involves exposing metal parts to a strong acid solution in order to remove surface deposits that may have formed, thereby preparing the surface for painting or other modification). There may be other ions in solution, but they are not acids or bases. In your analysis, ignore species that contain more than one Fe ion, both a Fe ion and a SO4 ion, or both a Ca ion and an SO4 ion. Using MINTEQ:
- Compute the amount of lime (Ca(OH)2), in mol/L, needed to bring the solution to pH 5.5 for discharge.
- Develop a titration curve for the process (pH vs. lime added) up to pH 10.