Adsorption characteristics of waste crab shells for silver ions in industrial wastewater

Waste crab shells were used as an adsorbent to efficiently adsorb silver ions in actual industrial wastewater. The functional groups like -NHCO or -NO2 groups in crab shells play an important role in the adsorption of silver ions. The highest removal efficiency was about 96% obtained from the 30 g/L of adsorbent concentration at initial pH 6.0 of waste solution. Langmuir sorption model was chosen to estimate the maximum uptake capacity and affinity constant of waste crab shells for silver ions, and its value was 5.21mg/g-dry mass and 0.411 L/mg, respectively. Entire adsorption process was completed in 60 min, and removal efficiency of crab shells was higher than that of Amberlite IR 120 plus resin. The effect of temperature could be neglected in the range of 15.0-45.0 A degrees C. Also, instrumental analysis such as SEM (scanning electron microscopy) photographs, EDX (energy dispersive X-ray) spectrum, and FT-IR spectrum were applied to investigate the surface condition and functional groups of crab shells.