CIVL375: Experiment REMOVAL OF ORGANIC CONTAMINANTS BY ACTIVATED CARBON Introduction Adsorption is a process which involves the interphase accumulation or concentration of substances at a surface or interface Adsorption may be a result of Van der Waals forces acting on the solid surface (physical adsorption) or due to chemical interaction between the solid and the absorbed surface Adsorption equilibrium is established when the concentration of the contaminant remaining in solution is in dynamic balance with that at the surface C S Several models have been established to describe adsorption behavior The Linear model S=KC The Fruendlich model (nonlinear sorption) S= k Cn The Langmuir behavior 1 1 = + S b ab C where K, k, n, a, and b are constants usually determined in the laboratory for each sorbate-sorbent combination Objectives The objectives of this exercise are to: become acquainted with batch reactors and determine the equilibrium sorption behavior that best describe the interaction of methylene blue with activated carbon in a batch reactor become acquainted with packed bed reactors and determine the amount of carbon needed to treat 120 m3/day of an industrial wastewater containing methylene blue at a concentration of Co Assume the allowable concentration before discharge of the wastewater is 0.2Co Sample Identification A synthesized sample containing methylene blue is generated for this exercise Materials and Reagents Glass bottles with caps Glass column with end fittings and tubes Pump Spectrophotometer Shaker Methylene blue Actived carbon Procedure Construct a calibration curve for the spectrophotometer using a wavelength of 660 nm This is usually accomplished by measuring instrument response for different prepared concentrations of contaminant (standards) Table: Data to construct calibration curve for methylene blue Std # Concentration mg/l response blank Determine the initial concentration (Co) of methylene blue in the solution to be treated Conduct a batch sorption isotherm study Use bottles to conduct a batch sorption isotherm study The initial concentration of the contaminant and volume of liquid are kept the same but the mass of activated carbon will be varied from (blank) to a maximum value given by the instructor Table: Data to construct sorption isotherm for methylene blue Bottle # Volume of Mass Initial Final solution V, carbon concentration response ml M, (g) Co, mg/L blank Final liquid concen tration C, mg/L Concentration on carbon S, mg/g The equilibrium concentration on the carbon is determined by mass balance: (Mass of contaminant in the liquid + mass of contaminant on the carbon)initial = (Mass of contaminant in the liquid + mass of contaminant on the carbon)final (C×V + S×M)initial = (C×V + S×M)final Co×V + = Cfinal×V + S×M Plot the sorption isotherm and determine the best-fit model (based on the value of r2) Perform a column experiment A Determine the following characteristics related to the column conditions •Length of the column (L) •Internal diameter of the column (D) •Mass of carbon (M)= Wt column filled with carbon – Wt column empty •Flow rate (Q) B Inject a solution containing methylene blue at a concentration of Co with a flow rate Q Use stop watch and mark this as zero time Collect samples from the other end of the column (effluent samples) and determine the Cout at different time intervals Table : Effluent concentration versus time t response concentration t response concentration C Generate a breakthrough curve for methylene blue The y-axis for this curve is Cout/Co and the x-axis is time From the graph determine the time required to reach to an allowable effluent concentration of 0.2 Co D Use scale-up approach (as presented in the lecture notes) to estimate the amount of carbon needed to treat 120 m3/day of this wastewater to meet the above allowable effluent concentration Note that due to time limitations, the column experiment is not commonly performed Requirements: Fill out the provided experiment data sheet and carry out the required calculations If you are requested to submit a report of this experiment then your report should contain (a) an introduction that ends with the objective (b) methodology including sample identification (c) results and discussion (d) conclusion (e) references and (f) an appendix that contains the filled data sheet CIVL 375: Experiment Data Sheet REMOVAL OF ORGANIC CONTAMINANTS BY ACTIVATED CARBON Name ID Experimental Conditions Experiment date Sample identification Initial concentration of methylene blue (mg/l) Mixing time (day) Instrument Calibration Standard No Batch Sorption Isotherm Bottle Activated carbon No mass (g) Concentration, mg/l Volume of methylene blue solution (ml) Response Response at equilibrium Concentration at equilibrium (mg/l) Required Calculations Construct a calibration curve for the detection of methylene blue using the spectrophotometer Plot the equilibrium solid concentration versus the equilibrium liquid concentration Determine the appropriate sorption model