Adsorption characteristics of Pb (II) on alkali treated tea residue

The alkali treated tea residue (ATTR) was used as a novel adsorbent to remove Pb (II) from aqueous solution. The adsorption characteristics and underlying adsorption mechanism of Pb (II) on ATTR were investigated. Scanning electron microscopy (SEM) showed that ATTR had a highly porous surface structure. Comparative studies showed that the removal rate of Pb (II) on ATTR was significantly higher than that on green tea and green tea residue. Batch studies revealed that the solution pH was the key factor affecting Pb (II) adsorption and the maximum pH for efficient adsorption was about 4.5, and the adsorption equilibrium could be obtained within 90 min, and the adsorption kinetic followed the pseudo-second-order model. From the Langmuir isotherm, the maximum adsorption capacity for Pb (II) was 64.10 mg/g at 25 °C. Fourier transform infrared spectroscopy (FTIR) analysis revealed that carboxyl and hydroxyl functional groups were mainly responsible for the adsorption of Pb (II). These suggested that the low-cost ATTR could be used as a potential and appealing adsorbent for the removal of Pb (II) from aqueous solutions.