Preparation and characterization of polyacrylamide / sodium alginate microspheres and its adsorption of MB dye

A novel polyacrylamide (PAM) / sodium alginate (SA) adsorbent with double network structure was prepared by emulsion polymerization of acrylamide (AM) and SA. The chemical structure, thermal stability, crystallinity, pore size and distribution, surface area, surface morphology and energy dispersive spectrum of PAM/SA microspheres were determined by FTIR, TGA, XRD, BET, SEM and EDS. In addition, the effects of pH, temperature and adsorbent dosage on the adsorption capacity of Methylene blue (MB) were evaluated. The adsorption isotherms and kinetics as well as the thermodynamics of adsorption process were also studied. The results show that due to the entanglements between PAM and SA molecular chains. A double network structure is formed. The introduction of SA leads to the decrease of thermal stability and crystallization ability of PAM. The pore size is in the range of 0-200 nm, and the mesoporous structure is uniform. The particle size of is in the range of 1-10 u m. The surface of PAM/SA composite microspheres is smooth, and the ion crosslinking point is uniformly distributed. The results show that when pH = 6, temperature is 25 degrees C and adsorbent dosage is 0.1g, the maximum adsorption capacity of PAM/SA composite microspheres is 75 mg/g. Langmuir isothermal model has better correlation with MB adsorption, and the maximum capacity obtained by simulation is 1070.54 mg/g. The pseudo-first-order kinetics and adsorption thermodynamics are better. The adsorption process is a physical adsorption rather than the chemical interation. The adsorption force decreases with the increase of temperature. The obtained PAM / SA composite microspheres have excellent adsorption capacity for dye removal from wastewater.