Article

Arsenic removal from contaminated soil using phosphoric acid and phosphate.

College of Resources and Environment, Central South University of Forestry and Technology, Changsha 410004, China.
Journal of Environmental Sciences (Impact Factor: 1.92). 02/2008; 20(1):75-9. DOI: 10.1016/S1001-0742(08)60011-X
Source: PubMed

ABSTRACT Laboratory batch experiments were conducted to study arsenic (As) removal from a naturally contaminated soil using phosphoric acid (H3PO4) and potassium dihydrogen phosphate (KH2PO4). Both H3PO4 and KH2PO4 proved to reduce toxicity of the soil in terms of soil As content, attaining more than 20% As removal at a concentration of 200 mmol/L. At the same time, acidification of soil and dissolution of soil components (Ca, Mg, and Si) resulted from using these two extractants, especially H3PO4. The effectiveness of these two extractants could be attributed to the replacement of As by phosphate ions (PO4(3-)). The function of H3PO4 as an acid to dissolve soil components had little effects on As removal. KH2PO4 almost removed as much As as H3PO4, but it did not result in serious damage to soils, indicating that it was a more promising extractant. The results of a kinetic study showed that As removal reached equilibrium after incubation for 360 min, but dissolution of soil components, especially Mg and Ca, was very rapid. Therefore dissolution of soil components would be inevitable if As was further removed. Elovich model best described the kinetic data of As removal among the four models used in the kinetic study.

0 Bookmarks
 · 
118 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Polymeric sponges coated with hydroxyapatite (S-HA) were used in lead and cadmium uptake experiments to study the sorption capacity for possible in situ metal remediation. S-HA metal sorption was compared with synthetic hydroxyapatite (HA) powder behavior to evaluate metal uptake efficiency. The coated sponges were produced by a two-step process consisting of monetite coating and further conversion to HA. Aqueous solutions containing nearly 1000 mg L− 1 of Cd2+ and 1000 mg L− 1 of Pb2+ were shaken for 24 hours with 0.4 g of each sample (HA and S-HA). The metal uptake experiments using polymeric sponges (S-HA) coated with HA accounted for nearly 96% of Pb2+ removal and 65% of Cd2+ removal after a 24-hour sorption experiment, while the hydroxyapatite (HA) powder sorbed 100% of Pb2+ and almost 50% of Cd2+. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses of polymeric sponges coated with HA after the Pb2+ uptake experiment showed needle-like crystals on the material surface, identified by X-ray diffraction (XRD) as pyromorphite, Pb10(PO4)6OH2. An initial stage of nucleation after Cd2+ uptake (24 hours) on the S-HA sample surface was observed by SEM images and EDS analysis, indicating formation of a new phase.
    Surface and Coatings Technology 02/2012; 206(s 11–12):2810–2816. · 2.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Colloidal gas aphron dispersions (CGAs) can be described as a system of microbubbles suspended homogenously in a liquid matrix. This work examines the performance of CGAs in comparison to surfactant solutions for washing low levels of arsenic from an iron rich soil. Sodium Dodecyl Sulfate (SDS) and saponin, a biodegradable surfactant, obtained from Sapindus mukorossi or soapnut fruit were used for generating CGAs and solutions for soil washing. Column washing experiments were performed in down-flow and up flow modes at a soil pH of 5 and 6 using varying concentration of SDS and soapnut solutions as well as CGAs. Soapnut CGAs removed more than 70% arsenic while SDS CGAs removed up to 55% arsenic from the soil columns in the soil pH range of 5-6. CGAs and solutions showed comparable performances in all the cases. CGAs were more economical since it contains 35% of air by volume, thereby requiring less surfactant. Micellar solubilization and low pH of soapnut facilitated arsenic desorption from soil column. FT-IR analysis of effluent suggested that soapnut solution did not interact chemically with arsenic thereby facilitating the recovery of soapnut solution by precipitating the arsenic. Damage to soil was minimal arsenic confirmed by metal dissolution from soil surface and SEM micrograph.
    Chemosphere 07/2014; 119C:355-362. · 3.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mining is a source of trace element contamination of neighbouring soils. This study determined the influence of soil amendments (iron oxides, Fe; organic matter, OM; and calcium phosphate, PCa) on arsenic uptake and translocation by tomato and parsley growth in an As-contaminated soil. The original contaminated soil without amendments was collected in the vicinity of the abandoned Santo António mine (Penedono, Portugal), which was a very important gold and arsenic mining centre in the middle fifties of the last century. An uncontaminated soil was also used as control. Growth parameters measured were plant height, length of 4th leaf (tomato only) and dry matter accumulation. Arsenic concentration in plant components was also determined, and human health risks related to the edible tissues were calculated. Results showed that arsenic availability in the soil varied with the amendments applied: OM and PCa increased arsenic availability, while the opposite effect was found with Fe (at 3 g kg− 1). Soil amended with iron oxides showed no positive effect on plant growth compared with the original soil with no amendments. Amongst all the amendments, OM led to the best results relatively to all growth parameters measured in tomato, including dry matter accumulation and fruit yield. Parsley growth was very small except in the PCa at 12 g kg− 1. Parsley translocated more arsenic to shoots, while tomato retained a greater proportion in roots. The health risk for adults and adolescents was within acceptable limits with an average weekly intake of 500 g of tomato and 20 g of parsley, although the arsenic concentration in edible tissues was still considerable greater than in plants grown in the uncontaminated control soil.
    Journal of Geochemical Exploration 12/2012; 123:114–121. · 2.43 Impact Factor

Preview

Download
4 Downloads
Available from