Study on the Effects of Cupressus sempervirens and Pinus pinaster-derived Adsorbents on Arsenic (III) Removal from Polluted Water

Abstract

The present study investigated the effects of Cupressus sempervirens (cypress) leaves, cones, bark and Pinus pinaster (pine) cone chips and bark on the removal of arsenic (III) from polluted water. The study aimed to observe the effects in the conditions close to the natural water systems, that is pH 6~7, room temperature, and using tap water for its high resemblance with water in the field in comparison to the deionized or distilled water with its pH adjusted with citric acid from lemon juice to avoid the addition of industrial chemicals (in fact, more likely unavailable to populations of concern). The effects of various adsorbents for the arsenic (III) removal were observed with regard to the following two parameters: adsorbent dose and arsenic initial concentration. The analysis showed that the removal efficiency increases in proportion to the adsorbent dose for cypress leaves, cones, bark and pine cone chips but decreases with the increase of the adsorbent dose for the pine bark. On the other hand, the removal efficiency hardly showed any relation with the arsenic initial concentration except for pine bark. Among the studied materials, cypress leaves exhibited a great potential in the removal of arsenic (III), followed by cypress cones and pine cones. Cypress bark and pine bark, on the contrary, showed precarious results. Equilibrium and kinetic experiments were conducted with cypress leaves as an adsorbent at the arsenic (III) initial concentrations of 0.1, 0.2 and 10 ppm, which was found to be the most efficient among the five types of studied adsorbents. Isotherm calculations showed that the adsorption of As (III) onto cypress leaves fitted both Langmuir and Freundlich models. And, kinetics studies indicated that the adsorption was better represented by a pseudo-2nd order system followed by intra-particle diffusion.