Layered double hydroxide loaded pinecone biochar as adsorbent for heavy metals and phosphate ion removal from water

This study modified pinecone biochar with a novel layered double hydroxide (LDH) to enhance its capacity to adsorb heavy metal and phosphate ions from water. The unmodified pinecone biochar demonstrated moderate adsorption capacities for Cu²⁺ (25.0 mg/g), Co²⁺ (24 mg/g), Pb²⁺ (22.9 mg/g), and phosphate (36.0 mg/g). However, after LDH modification, the LDH-biochar showed significantly improved adsorption capacities for Pb²⁺ (135.9 mg/g) and phosphate (160.8 mg/g) and a slight increase for Cu²⁺ (30.6 mg/g) and Co²⁺ (28.0 mg/g). The LDH layer enhances the adsorption of Pb²⁺ through ion exchange, phosphate through surface precipitation, and Cu²⁺ and Co²⁺ through surface complexation. The integration of LDH creates a multifaceted layer that utilizes various mechanisms to boost the biochar's adsorption capacity.