Department of Civil Engineering-I.I.T. Delhi CVL722 1st Semester HW Set2. Adsorption

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Department of Civil Engineering-I.I.T. Delhi CVL722 1st Semester 2016-17 HW Set2 Adsorption Q1: For the following information, determine Langmuir and Freundlich model constants?

[20 points] See class example; See which model describe the data well in graph paper.

1 Department of Civil Engineering-I.I.T. Delhi CVL722 1st Semester HW Set2 Adsorption Q1: For the following information, determine Langmuir and Freundlich model constants? Also plot Q of these models with equilibrium adsorbate concentration ranging from 0 to 10 mg/l? Compare these two models and comment on their suitability in describing the observation? [20 points] See class example; See which model describe the data well in graph paper. Q2: For the following information, determine Langmuir model constants and adsorption capacity of alumina for initial anthracene concentration equal to moles/l? Also plot Q vs. C (t) for C (t): 0 to 10 moles/l and comment on it. Q=Qmax*KC/[1+KC] so Qmax*K=22; K=375 L/mol; Qmax=22/375 (mol/kg) C[0]= mol/l; Ceff=? Q=[C0-Ceff]*V/[XV] say 1 kg alumina was used in 1 liter sample. Q=[C0-Ceff] (mol/kg) = 22Ceff/[1+375Ceff] solve for Ceff; calculate % removal now; adsorption capacity of alumina = Q=[C0-Ceff]*V/[XV]= [C0-Ceff] (mol/kg)

2 Q3. What is the difference between Langmuir and Freundlich adsorption isotherm mechanisms? See lecture notes Q4. Untreated drinking water has 0.02 mg/l of geosmin, which gives earthy odor. How much removal can be achieved by adding 10 mg/l powdered activated carbon (PAC) in water? Assume geosmin adsorption on PAC is defined by Freundlich adsorption Q eq = K f (C eq ) 1/n where Qeq is mass of geosmin adsorbed on PAC (µg) per mg of PAC; C eq is concentraton of dissolved geosmin in water (µg/l), and K f = 0.5 (µg/mg)(l/ µg) (1/n) and (1/n)=1.08. See approach used in Q2; here X=10 mg/l is given; reactor volume =1 liter; C0=0.02 mg/l Ceff=? determine Ceff and then calculate % removal Q5. How does adsorption happen? Differentiate between competitive and cooperation adsorption? See lecture notes; in competitive adsorption-two ions compete for same adsorption sites and one ion might not get completely adsorbed on sites (ex: reduction in adsorption of arsenate ions due to sulphate ions on iron oxide sites); in cooperation adsorption-one ion cooperate with other ion and increase its adsorption on adsorbent (ex: Calcium ions increase adsorption of arsenate ions on iron oxide sites) Q6. What is the difference between Langmuir and Freundlich adsorption isotherm mechanisms? What do these models indicate about adsorption capacities of adsorbent? Can these models provide information on homogeneity or heterogeneity of adsorption sites? See lecture notes Q7. How does drawing a breakthrough curve help in deciding time for changing of activated carbon packed in activated carbon-based absorber? See lecture notes Q8. Draw a breakthrough curve and label all important information one can obtain from this curve. Can this curve be used in setting time for changing adsorbent in absorber? See lecture notes

3 Q1. Groundwater contaminated with TCE is treated with powdered activated carbon by sorption. The adsorption of TCE on PAC follows a Freundlich isotherm model as per following equation Q eq = 129(C eq ) 0.73 where Qeq is mass of TCE adsorbed on PAC (mg/g PAC); C eq is concentration of dissolved TCE in water (mg/l). (i) If TCE concentration in water is 1 mg/l, what mass of PAC must be used per volume of water (mg PAC/L water) to reduce TCE concentration to the allowed maximum contaminant level of mg/l? (ii) if the amount of PAC applied is only half of what is calculated in part (i), what is the equilibrium aqueous concentration of TCE? Q2. How does adsorption happen? Differentiate between competitive and cooperation adsorption? Q3. What is the difference between Langmuir and Freundlich adsorption isotherm mechanisms? What do these models indicate about adsorption capacities of adsorbent? Can these models provide information on homogeneity or heterogeneity of adsorption sites? Q4. Untreated drinking water has 0.02 mg/l of geosmin, which gives earthy odor. How much removal can be achieved by adding 10 mg/l powdered activated carbon (PAC) in water? Assume geosmin adsorption on PAC is defined by Freundlich adsorption Q eq = K f (C eq ) 1/n where Qeq is mass of geosmin adsorbed on PAC (μg) per mg of PAC; C eq is concentration of dissolved geosmin in water (μg/l), and K f = 0.5 (μg/mg)(l/ μg) (1/n) and (1/n)=1.08. Q5. How does drawing a breakthrough curve help in deciding time for changing of activated carbon packed in activated carbon-based absorber? Q6. Draw a breakthrough curve and label all important information one can obtain from this curve. Can this curve be used in setting time for changing adsorbent in absorber? Q7. Fit Langmuir and Freundlich adsorption isotherm model for adsorption data of Sand_110 (initial arsenic concentration = 1mg/L). Calculate values of Qmax (mg/g) and (b) (L/mg) and coefficient of determination (R2) for this model fitting and comment on model effective of explaining this data? Media Ceq Qt Ceq/Qeq Ceq g/l ug/l mg/g g/l mg/l

5 Q8. Comment on adsorption capacity of activated carbon for following 3 pesticides? (model: Freundlich model; Qe= adsorption capacity and Ce=equibirium capacity) Q9. Compare removal kinetics of different pesticides on activated carbon?

6 Q10. Compare arsenic adsorption isotherm patterns for Fig (a) high concentration range in distilled ionized water and for Fig (b) low concentration range in distilled ionized water? Q11. Describe adsorption mechanisms as per following schematic for adsorption on porous activated carbon material.

7 Disinfection Q1. The Chick s Law: For disinfection, assume N (0) is initial number of pathogens and N (t) is remaining number of pathogens at time and given by N(t)=N(0)* exp(-k*t) where K is disinfection rate (unit=1/unit of time) and depends on disinfectant-pathogen interaction and solution characteristics. Here R-log removal: R=-log 10 [N(t)/N(0)] If disinfectant concentration (C disinfectant ) and contact time (t c ) are related to each other by following equation (the Watson s Law): (C disinfectant ) n * (t c ) = constant (standard unit: C in mg/l and t c in minute) (i) (ii) Calculate R-log removal value for 99.9% removal? What is the remaining pathogen concentration at this removal after 1 minutes of contact time? (Assume K=0.046/min) Now assume C (mg/l)*t (minute) = 100 minute *mg/l corresponds to 2-log removal, calculate value of K (assume chlorine concentration (C) used here = 1mg/L)? (iii) At a chlorine dose = 1mg/L and contact times varying between 1 minute to 100 minutes (in 5 minutes increment), plot fraction of the pathogen killed with contact time and determine minimum contact time required for at least 99.99% removal? (use K value from part (ii)) Q2. Calculate the quantity of chlorine consumed/day for 3-log removal of rotaviruses from secondary effluent (ph7), where free chlorine residual is 2 mg/l, the first-order decay rate of chlorine is 0.2/h and flow rate is 1000m 3 /day. Given that Ct value is 243 for ph7.0. [15 points] Q3. Name three disinfection kinetics models generally used to model disinfection process. Can CT concept be applied to all three kinetic models? Why or why not? [10 points] Q4. Refer Figure 1 for wastewater consists of ammonia, organic matter and microorganisms) Chlorine dosage (mg/l) Chlorine residual (mg/l) (i) Discuss the significance of different regions. [8 points] (ii) Calculate chlorine dose to achieve 0.75 mg/l free available chlorine? [4 points] Q5. Look at the following relationship between concentration of free residual chlorine and contact time required for 99% kill (Watson s Law: C 0.86 t p = λ (constant) for different pathogens). Pathogen type Adenovirus 3 E.coli Coxsackievirus A2 λ (constant) For given chlorine dose, how long would you like to disinfect to achieve maximum removal of all pathogens? Explain the result. [6+4=10 points]

8 Q1. Untreated drinking water has 0.02 mg/l of geosmin, which gives earthy odor. How much removal can be achieved by adding 10 mg/l powdered activated carbon (PAC) in water? Assume geosmin adsorption on PAC is defined by Freundlich adsorption: Q eq = K f (C eq ) 1/n where Qeq is mass of geosmin adsorbed on PAC (µg) per mg of PAC; C eq is concentration of dissolved geosmin in water (µg/l), and K f = 0.5 (µg/mg)(l/ µg) (1/n) and (1/n)=1.08.[8 points] Q2. Draw a breakthrough curve and label all important information one can obtain from this curve. [4 points] Q3. Calculate the quantity of chlorine consumed/day for 3-log removal of rotaviruses from secondary effluent (ph7), where free chlorine residual is 2 mg/l, the first-order decay rate of chlorine is 0.2/h and flow rate is 1000m 3 /day. Given that Ct value is 243 for ph7.0. [8 points]

CEL 795- Water and Wastewater Treatment Unit Processes 1 st -Semester Disinfection Dr. Arun Kumar

CEL 795- Water and Wastewater Treatment Unit Processes 1 st -Semester 2011-2012 Disinfection Dr. Arun Kumar (arunku@civil.iitd.ac.in) Courtesy: Dr. Irene Xagoraraki (MSU, USA) Disinfection Water is often