Removal of phenolic compounds from rubber–textile wastewaters by physico-chemical methods

Removal of phenolic compounds from rubber–textile wastewaters (RTWWs) by physico-chemical process was investigated by using four different types of coagulants (Al2(SO4)3, Fe2(SO4)3, FeSO4, FeCl3) with or without lime (Ca(OH)2) addition, in jar-test experiments. The RTWWs of the present tire-cord fabric plant may contain seven different types of dipping solutions (DSs), which provide an adhesive property to the fabric. The optimum results were obtained by using 50% FeCl3 solution and lime at various dosages at 23 °C, which satisfy the decision criterion of high treatment efficiency (TE) in removing the phenolic compounds, good settling rate (SR) of the flocs, and a reasonably low cost of treatment. The achieved treatment efficiencies are over 94% in most of the cases. First adding lime and then the coagulant yield better results in terms of the treatment efficiency and settling behavior of the formed flocs. One minute rapid mixing after the addition of lime and coagulant, followed by 30-min gentle mixing were applied in the experiments successfully. The TE of the process, and the settling rate (SR) of the flocs decrease with the decreasing solution-temperature (from 23 to 15 °C), in using FeCl3 as coagulant with the addition of lime. Under these circumstances, the optimum pH of coagulation is found to be around 12.