MEASUREMENT OF SORPTION ISOTHERMS WITH FLOW-THROUGH REACTORS

A simple flow-through reactor technique is described for measurements of sorption isotherms on solid environmental materials such as soils, crushed rocks, aquifer materials, or peat. The applicability of the me thod was established by determining copper sorption isotherms at effec tively constant pH for two different soil samples. The experimental re sults compare favorably with independent batch and column studies. Pot ential advantages of the flow-through technique are exemplified by stu dying the sorption behavior of one soil sample that shows in batch exp eriments a pronounced dependence on the solid concentration (particle concentration effect). Comparison of these results with the flow-throu gh reactor technique and independent column experiments confirms unequ ivocally that in this case the influence of the solid concentration is an artifact due to insufficient prewashing of the soil with the backg round electrolyte solution and has nothing to do with the shaking proc ess in batch experiments. The present results indicate that incomplete removal of preadsorbed ions may often represent a major source of err or in sorption studies and may be difficult to recognize in batch expe riments.