Carbonell-Barrachina A, DeLaune R D, Jugsujinda A
División Tecnología de Alimentos, Departamento Tecnología Agro-Alimentaria, Universidad Miguel Hernández, Alicante, Spain.
Waste Manag. 2002;22(6):657-65. doi: 10.1016/s0956-053x(01)00044-7.
Phosphogypsum (PG), primary byproduct from phosphoric acid production, is accumulated in large stockpiles and occupies vast areas of land. Contaminants emanating from PG stacks can impact the environment including waterbodies. The major constraint for PG use in the environment is the presence of metals in high concentrations. Reduction of sulfate found in PG and significance of sulfide production in reducing aqueous concentrations of toxic metals were studied. Mississippi River alluvial sediment amended with PG was equilibrated under controlled redox (-250 mV) and pH (5.5, 6.5, and 7.5) conditions. Phosphogypsum addition resulted in a large increase in sulfide levels in sediment suspensions. As a result, the solubility of spiked heavy metals (Cd and Cr, 100 and 1000 mg kg(-1)) and natural trace elements (As, Ba, and Cd) was significantly reduced by precipitation as insoluble sulfides. Sediment pH also influenced sulfate reduction and sulfide formation in both PG-amended and control sediment. Low sediment pH (5.5) resulted in the highest release of all studied metals and sulfate into sediment solution. This study indicates that if PG or PG-products are placed in neutral to alkaline sediments/soils and/or reducing environments, metals released at toxic levels should be of little concern to the wetland environment.
磷石膏(PG)是磷酸生产的主要副产品,大量堆积且占用大片土地。PG堆场排放的污染物会影响包括水体在内的环境。PG在环境中应用的主要限制因素是其含有高浓度金属。研究了PG中硫酸盐的还原以及硫化物生成对降低有毒金属水溶液浓度的意义。用PG改良的密西西比河冲积沉积物在受控的氧化还原(-250 mV)和pH(5.5、6.5和7.5)条件下达到平衡。添加磷石膏导致沉积物悬浮液中的硫化物水平大幅增加。结果,添加的重金属(镉和铬,100和1000 mg kg⁻¹)以及天然微量元素(砷、钡和镉)的溶解度因形成不溶性硫化物沉淀而显著降低。沉积物pH也影响了PG改良沉积物和对照沉积物中的硫酸盐还原和硫化物形成。低沉积物pH(5.5)导致所有研究的金属和硫酸盐向沉积物溶液中的释放量最高。这项研究表明,如果将PG或PG产品置于中性至碱性沉积物/土壤和/或还原环境中,以有毒水平释放的金属对湿地环境应几乎没有影响。