Pb2+ Adsorption, Performance, and Response Surface Optimization of Hydroxyapatite Nanowire Sodium Alginate Aerogel (HSA)

A novel composite biomass aerogel adsorbent (HSA) was prepared by dual physical and chemical cross-linking using sodium alginate (SA) as an organic biomass template and hydroxyapatite nanowires (HAPNWs) as an inorganic biomass skeleton. The structure of the HSA was characterized by scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), Fourier transformed infrared spectroscopy (FTIR), and stress testing. One-factor experiments were conducted focusing on adsorption conditions at a Pb ion concentration of 300 mg/L, and the adsorption conditions were optimized using the response surface method. The optimal conditions obtained by numerical optimization using Design-Expert 13 were as follows: pH of 7.23, adsorption temperature of 35.42 °C, and adsorption time of 1050.73 min; the optimal adsorption capacity was 278.874 mg/g. To further reveal the adsorption mechanism of HSA, its adsorption model and kinetics were analyzed. Adsorption was most consistent with the Langmuir isothermal adsorption model, while the kinetics were most consistent with the pseudo-secondary kinetic model. R2 reached 0.9986, indicating a mono-molecular layer of adsorption by heat, while the main adsorption mechanism was chemisorption.