We first revealed the behavior and biochemical mechanism of high iron attapulgite (HIAP) different dosages affecting sewage sludge (SS) composting. HS/TOC ratio increased, but HA/TOC HA/FA ratios reduced with increase in HIAP dose. High-dose promoted formation more HS by weak catalytic effect could bind FA than HA strong adsorption to inhibit polymerization adsorbed into HA. Mixing SS subsequen...