Ash from poultry feather gasification was investigated as an adsorbent for Cd removal from synthetic wastewater under a range of operational conditions: initial pH (2–8) and salinity (8–38 mS/cm) of wastewater, ash dosage (2.5–50 g/L), Cd concentration (25–800 mg/L) and contact time (5–720 min). The ash was highly alkaline and had low surface area and micropores averaging 1.12 nm in diameter. Chemical/mineralogical analysis revealed a high content of P2O5 (39.9 wt %) and CaO (35.5 wt %), and the presence of calcium phosphate, hydroxyapatite and calcium. It contained only trace amounts of heavy metals, BTEX, PAHs and PCBs, making it a safe mineral by-product. Cd adsorption was described best with Langmuir and pseudo-second order models. At pH 5, an ash dosage of 5 g/L, 40 min contact time and 100 mg Cd/L, 99% of Cd was removed from wastewater. The salinity did not affect Cd sorption. The maximum adsorption capacity of Cd was very high (126.6 mg/g). Surface precipitation was the main mechanism of Cd removal, possibly accompanied by ion exchange between Cd and Ca, coprecipitation of Cd with Ca-mineral components and Cd complexation with phosphate surface sites. Poultry ash effectively removes high concentrations of toxic Cd from wastewater.

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