Reference no: EM13865777

Assume a wastewater contains a high soluble Cu II concentration. Determine the pH where the minimum solubility of Cu(OH)₂ occurs, assuming a constant total nitrogen (N_T) concentration (NH₄⁺ and NH₃) of 100 mg/l as N. At this pH, what is the total soluble copper concentration (mg/L)?

Neglect ionic strength corrections and assume the solution temperature is 25°C. The appropriate cumulative equilibrium formation constant expressions for metal complexes with inorganic ligands (OH^-1 and NH₃) which affect the solubility of the Cu II system are readily available in Lange's Handbook of Chemistry, along with the remaining equilibrium relationships: solubility product (K_sp) for Cu(OH)₂, ionization constant (K_a) for the NH₄⁺/ NH₃ couple.

Utilize the first four cumulative formation constants (K's) for each ligand (OH^-1 and NH₃) in your calculations. Calculate the Cu concentrations from pH 6 to 12 with increments of 0.25 pH units with and without the NH₃ and plot both results on the same graph.

Recall that for a monoprotic species the distribution coefficient is given by α₁ = {1/(1+([H₊]/K_a))}, where [NH₃] = α₁{N_T}.