Identification of transfer mechanisms involved in soiled CIP solutions regeneration at extreme pH and high temperature

Processing soiled cleaning in place (CIP) solutions induces large economic and environmental costs. Hence, recycling such solutions appears as an attractive alternative to reduce these costs. Recycling requires that a suitable green process is set which take into account the extreme physicochemical conditions prevailing during the cleaning of equipments of food or textile industries. Unfortunately, most of the processes used so far for water treatment are not efficient at high temperature (80–90 °C) or extreme pH (pH 1 and 14) which are commonly encountered in CIP. Purposely, Na-bentonite, in its crude or activated forms, was used to evaluate its potential for organic and mineral matter removal from such solutions. The resulting adsorption isotherms acquired at two temperatures, various pH values and salt concentrations were analyzed through the Langmuir, Freundlich and BET models. It is concluded that Na-bentonite action is based on a combination of adsorption and carrying capacity, the latter being related to its ability to coagulate at extremes pH. The efficiency of this innovative regeneration process combining adsorption/coagulation and flocculation was successfully tested by using synthetic industrial solutions mimicking those found in the dairy industry.

► Soiled dairy CIP solutions were regenerated using crude and modified Na-bentonite.
► The modeling approach was applied to estimate the adsorption isotherm parameters.
► Clay purification action is due to both the adsorption and the carrying capacities.
► Clay purification capacity was enhanced with the increase medium’s ionic strength.
► The treatment capacity of clays was reduced at high temperature.