土木与环境工程学报

Expansive soil deposits in the study area imposed multiple problems to various civil structures and require geotechnical solutions. The main objective of this study was to evaluate the possibility of utilizing waste marble dust and volcanic ash as soil stabilizers which are plentifully available in the vicinity. The evaluation was carried out with the addition of a predetermined percentage of the stabilizers up to 30% by mass measurement. The effects of the stabilizers on the different properties of the in-situ expansive soil sample were evaluated via experiments. The investigation showed that the physical properties and selling characteristics of the problematic soils have been improved significantly. Therefore, this study indicated that both waste marble dust (marble by-product) and volcanic ash (locally available material) can be used as stabilizers. It is also observed that the waste marble dust is more effective stabilizer than the volcanic ash for stabilizing the expansive soils of the study area due to the high concentration of calcium in the waste marble dusts. In the process, a base exchange occurs with the calcium ions of waste marble dust replacing sodium on the surface of the expansive clay particle.

This study aimed to prepare AC from flax straw and investigate its potential for the removal of Pb (II) ions from aqueous solution and real industrial wastewater. AC was prepared by chemical activation method using H₃PO₄ as activating agent. The effects of initial Pb (II) ion concentration, adsorbent dose, contact time and pH on the removal efficiency were studied by using aqueous solution prepared from Lead nitrate (Pb (NO₃)₂) on a batch mode. Response surface methodology was used in order to carry out experimental runs. The collected wastewater sample was characterized before and after treatment according to APHA methods. Activated carbon was characterized and results showed that the flax straw AC had 8.04% of moisture, 6.04% of ash, 18.615% of volatile matter, 79.421% of fixed carbon, 459.807 mg/g of iodine number and surface area of 489.455 m²/g. Physico-chemical characteristics showed that raw wastewater had a concentration of 3.95 mg/L Pb (II), 158.52 mg/L BOD5, 2482 mg/L COD, and 652.667 mg/L TSS. The highest removal efficiencies of Pb (II) metal ion which was achieved from aqueous solution and paint wastewater were found to be 95.16% and 78.73%, respectively. The experimental data are fitted with pseudo-second order model and adsorption of Pb (II) on flax straw AC fits the model of Langmuir very well. The results of the study suggested that flax straw AC can be used as an adsorbent for the removal of Pb (II) ion from industrial wastewaters.