Abstract: Composite of slag from garbage incinerators and residual sludge from wastewater treatment plants is proved to be a cost-effective absorbent adsorbent high in P adsorption capacity. This technology has opened up a field for recycling of the slag and sludge. Compared with the Freundlich model, the Langmuir model could better simulate phosphorus adsorption capacity of the adsorbent. Calculation using the Langmuir model shows that maximum phosphorus adsorption capacity of the adsorbent varied with ratio of its composition. It was 27300 and 13750 mg•kg^-1, 54.6 and 27.5 times greater than that of zeolite, respectively, when its composition ratio was 4:1 and 1:1. The composite absorbent adsorbent was significantly lower than zeolite in P desorption rate. Neither initial P concentration nor pH in the solution had much effect on P desorption rate of the composite adsorbent, indicating that the composite adsorbent was is applicable to solutions wide in pH range. Extraction tests show that the absorbent adsorbent is low in heavy metal extraction rate, safe to the environment and good in performance. To sum up, the composite adsorbent composed of slog from garbage incinerators and sludge from wastewater treatment plants is both high in P adsorption capacity and saturated adsorption, but low in desorption rate. It is, therefore, an ideal phosphate adsorbing filling.

Key words: composite adsorbent, garbage incinerator slag, residual sludge, isothermal absorption equation, desorption, heavy metal extraction