The Removal of Hg (II) Ions from Laboratory Wastewater onto Phosphorylated Haloxylon ammodendron: Kinetic and Equilibrium Studies

Haloxylon ammodendron (HA), a desert plant residue, has been utilized as adsorbent material for the removal of Hg (II) ions from laboratory wastewater after treatment with phosphoric acid to form Haloxylon ammodendron cellulose phosphate (HACP). Three levels of HACP having different phosphorous content were prepared. The HACP samples were characterized by estimating the phosphorous content as well as FT-IR spectra. Using the batch experimental systems, the removal of Hg (II) on the HACP particles was investigated. The data of the adsorption isotherm was tested by the Langmuir, Freundlich and Temkin models. The removal processes of Hg (II) onto HACP particles could be well described by pseudo-second order model. The adsorption rate of mercury was affected by the initial heavy metal concentration, initial pH, adsorbent dose and agitation time and temperature as well as extent of modification. The adsorption experiments indicated that the HACP particles have great potential for the removal of Hg (II) from laboratory wastewater. The maximum adsorption capacity (Q_max) of the HACP towards Hg (II) ions was found to be 384.6 and 416.7 and 476.2 mg/g at 30, 40 and 50°C, respectively. Similarly, the Freundlich constant, n values were found to be 6.6, 4.4 and 3.8 at 30, 40 and 50°C, respectively. The thermodynamics constants of the adsorption process: ΔH°, ΔS° and ΔG° were evaluated.