Poly(1,5-diaminonaphthalene) microparticles with abundant reactive amino and imino groups on their surface were synthesized by one-step oxidative polymerization of 1,5-diaminonaphthalene using ammonium persulfate as the oxidant. The molecular, supramolecular, and morphological structures of the microparticles were systematically characterized by IR and UV-vis spectroscopies, elementary analysis, wide-angle X-ray diffractometry, and transmission electron microscopy. The microparticles demonstrate electrical semiconductivity and high resistance to strong acid and alkali, and strong adsorption capability for lead(II), mercury(II), and silver(I) ions. The experimental conditions for adsorption of Pb(II) were optimized by varying the persulfate/monomer ratio, adsorption time, sorbent concentration, and pH value of the Pb(II) solution. The maximum adsorption capacity is 241 mg·g-1 for particles after a 24 h-exposure to a solution at an initial Pb(II) concentration of 29 mM. The adsorption data fit a Langmuir isotherm and follow a pseudo-second-order reaction kinetics. This indicates a chemical adsorption that is typical for a chelation interaction between Pb(II) and amino/imino groups on the sorbent. Graphical abstract Poly(1,5-diaminonaphthalene) microparticles with abundant functional amino and imino groups have been synthesized by one-step direct polymerization of non-volatile 1,5-diaminonaphthalene in aqueous medium for sustainable preparation of high-performance adsorbents to strongly adsorb lead(II), mercury(II), and silver(I) ions.
Keywords: 1,5-diaminonaphthalene polymer; Amino polycondensate; Lead ion removal; Mercury ion sorption; Metal chelate; Oxidative polymerization; Particle adsorbent; Polyaniline derivative; Silver recovery; Water purification.