Implementation of integrated Palygorskite with copper–aluminum layered double hydroxides composite in superior nitrate pollutant removal from wastewater

Environmental pollution with nitrate is a major issue of concern these days. Nitrate form highly stable nitrogenous compounds due to the extreme usage of nitrate fertilizers. However, most water treatment methods are ineffective in terms of nitrate removal and generation of secondary wastes as well. Consequently, this investigation is directed to assemble a novel, sustainable and ecofriendly Palygorskite (Fullers earth)-immobilized-Cu²⁺/Al³⁺ LDHs (Pal₅₀₀@Cu²⁺-Al³⁺ LDHs) composite. Removal of 10.0 - 20.0 mg L^-1 NO₃^– were thoroughly investigated and significantly concluded that pH 3.0, time 50 min, temperature 25 °C and 10 mg composite are the optimum conditions. The removal of NO₃^– by Pal₅₀₀@Cu²⁺-Al³⁺ LDHs was accomplished by a combination of pseudo-first-order model and Bangham expressions. Additionally thermodynamic parameters confirmed NO₃^– removal via exothermic and spontaneous adsorption process including a dissociative mechanism. The interaction and binding modes of NO₃^– ions to Pal₅₀₀@Cu²⁺-Al³⁺ were proposed via ion-pair interaction and anion-exchange mechanisms. Additionally, 200 and 250 mg of Pal₅₀₀@Cu²⁺-Al³⁺ LDHs exhibited excellent NO₃^– recovery from real agricultural drainage wastewater providing 81.0 and 98.0 %, respectively. Moreover, the explored Pal₅₀₀@Cu²⁺-Al³⁺ LDHs afforded good stability towards adsorption and desorption regeneration processes up to five successive cycles. Consequently, the collected results from this study verify the validity of Pal₅₀₀@Cu²⁺-Al³⁺ LDHs for exceptional removal of NO₃^– from real agricultural drainage wastewater.