Enhanced Phosphate Removal by Hydrated Lanthanum Oxide-Modified Quaternized Polyaniline Nanocomposite: Performance and Mechanism

Phosphorus mainly exists in the form of phosphate in water. Excessive phosphorus can cause eutrophication, leading to algae reproduction and the depletion of oxygen in water, destroying aquatic ecology. This study prepared quaternized polyaniline (PN) and quaternized polyaniline with lanthanum hydrate (HLO-PN), and a new nanocomposite for removing phosphate from wastewater was proposed. The results of adsorption experiments show that HLO-PN can effectively remove phosphate in the range of pH 3~7; the maximum adsorption capacity is 92.57 mg/g, and it has excellent anti-interference ability against some common coexisting anions (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi mathvariant="normal">F</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>,</mo></mrow></semantics></math></inline-formula> <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi mathvariant="normal">C</mi><mi mathvariant="normal">l</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>,</mo></mrow></semantics></math></inline-formula> <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>NO</mi></mrow><mrow><mn>3</mn></mrow><mrow><mo>−</mo></mrow></msubsup><mo>,</mo></mrow></semantics></math></inline-formula> <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>SO</mi></mrow><mrow><mn>4</mn></mrow><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula>) other than <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>CO</mi></mrow><mrow><mn>3</mn></mrow><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula>. After five adsorption–desorption cycles, the phosphate adsorption capacity (60 mg/g) was still 74.28% of the initial adsorption capacity (80.85 mg/g), indicating that the HLO-PN nanocomposites had good reusability and recovery of phosphorus. The characterization results show that phosphate adsorption is realized by electrostatic adsorption and ligand exchange.