between about 11 5 and 12 the temperature during this step should be from between about 50 u00b0 and 120 u00b0 c and preferably between about 70 u00b0 and 100 u00b0 c the contact time between process water and pulp can be very short at optimum conditions the time can be shorter than about 1 second but slightly longer times such as from about 1 6 seconds are generally better longer reaction times such as from about 0 1 6 min can also be applied but doing so does not appreciably affect the result a time exceeding 1 5 min therefore is normally of no interest the reaction time is normally determined by the nature of the washing equipment being used very short stay times can thus be achieved both during the usage of a washing press and a washing filter in the second washing step 6 at an alternative method only a partial flow of the pulp is utilized for separating the metal ions from the wastewater in the first washing step it is of course also possible to use an unbleached pulp which is not intended to be bleached or a reject pulp flow for separating the metal ions it is further possible to utilize the metal.