JWSS - Journal of Water and Soil Science

The concern about the war and the threat of terrorism and weapons application and prohibited weapons is growing; on the other hand, the contamination of soil, plant and disease outbreaks in the community is increasing. The main problem with crops, especially wheat in the contaminated soils of war zones, are associated with the high concentrations of heavy metals and toxic things, especially arsenic. Zeolite is one of the solutions to the problem of contaminated soils in war affected areas. The aim of this study was to determine the effect of the ionic strength of zeolite on the adsorption of arsenic and nutritional properties of wheat in contaminated soils including weapons. The experiment was carried out in a  factorial arrangement involving  a randomized complete design with three replications. Treatments included four levels of zeolite 2.5 (a₄), 1.5 (a₃), 0.5 (a₂), 0 (a₁) percent of the weight of the soil and two soil recourses, one obtained from out of the war zone (without contamination) (b₁) and other one was from the contaminated soil to weapons (b₂). The results showed that soils contaminated by weapons increased the concentrations of arsenic in wheat. Also, with the application of Zeolite in the contaminated soil treatments, there was a significant reduction at 1% level and a remarkable increase in nitrogen, phosphorus, potassium and calcium in the wheat grain in both soils.

Alginate biopolymer, due to possessing a high capacity and affinity for heavy metals, is a suitable material for the removal of metals from polluted waters; however, the weak structural consistency of alginate hydogels limits the practical application of this natural polymer in water purification practices. In this study, sepiolite clay mineral was used as a solidifier of alginate hydrogel to produce hybrid materials with different clay:alginate ratios (1:2, 1:4 and 1:8). Subsequently, the sorption of Pb by the prepared hybrid materials was studied in different Pb concentrations (25 to
2000 mg/L) and temperatures (15, 25, 35 and 45 °C). The results showed that the Langmuir and freundlich equations could significantly describe Pb sorption data on the sorbents. Based on the Langmuir model estimation, alginate showed and sepiolite showed the highest and lowest capacities for Pb sorption, respectively; also, the hybrids were intermediates in this respect. The capacity and affinity of all sorbents were enhanced with increasing the temperature from 15 to 45 °C. Standard enthalpy changes (ΔH°) were found to be positive, confirming that the process of Pb sorption on the sorbents was endothermic. Positive values were also obtained for the standard entropy changes (ΔS°), suggesting increased randomness at the solid-solution interface during the sorption of Pb ions on the sorbents. The values of the standard free energy change (ΔG°) were negative for all different temperatures, thereby indicating that sorption on the sorbents was spontaneous and favorable. Overall, it could be concluded that modification of alginate with sepiolite might cause the decreased sorption capacity of alginate; however, the hybrid materials are good candidates for the Pb removal from aqueous solutions because of their high sorption capacities.