Pharmaceuticals in the natural environment can be potentially toxic to living or

Question

Pharmaceuticals in the natural environment can be potentially toxic to living organisms. As a result, recent research is exploring this problem. Amoxicillin (Ax) is a widely used penicillin-like antibiotic. When released into the aquatic environment through sewage treatment plant discharges, some of the amoxicillin remains in the water phase, but it is also subject to sorption onto the particulate matter of the sewage sludge and biodegradation. The concentrations of amoxicillin in these three phases are functions of time and can be represented by: A moles Ax in water / L water concentration of amoxicillin in water phase S = moles Ax sorbed / g part concentration of amoxicillin sorbed onto particles g D = moles Ax degraded in water / L water concentration of amoxicillin degradation products and the particle loading in the waste stream, Q, can be represented by: Q = - g part / L water Note that multiplying Q by S gives the sorbed phase amoxicillin concentration in the same units as its concentration in the water and the concentration of its degradation products. At time t = 0, all of the amoxicillin is in the water. This initial concentration is represented by A_0. Once in the water phase, however, amoxicillin engages in reversible sorption and biodegradation so that the total mass introduced at time t = 0 is distributed between the water, particulate, and degraded phases. Assuming amoxicillin exists only in the water and particle phases, then, by conservation of mass: A_0 = A + Q S + D

Explanation / Answer

Solution:

Eq A.

A0 = A+QS+D

substituting the representations for A,Q,S and D. we get,

A0 = [moles Ax in water / L water] + [g part / L water] [moles Ax sorbed/ g part] + [moles Ax degraded in water / L water]

Now by solving, we get

A0 = [moles Ax in water + moles Ax sorbed + moles Ax degraded in water] / [L water]

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