JWSS - Journal of Water and Soil Science

Fruits and citrus wastes are generated in the food industry in large quantities. Their management in Iran, as one of the major hubs of fruits and citrus production, is of great importance. In this study, the biochar samples were prepared from pomegranate, orange and lemon peel waste produced in a juice factory using the pyrolysis process in the range of 400-500 °C; then their efficiency for zinc adsorption from an aqueous solution was investigated. The kinetic and isotherm data of zinc adsorption were fitted by the linear and nonlinear forms of the Langmuir and Frendlich isotherm models and the first-order and second-order pseudo-kinetics models. The results showed that under the experimental conditions applied, the maximum amount of zinc absorption by biochars derived from pomegranate, orange and lemon peel was 2.42, 1.83 and 3.17 mg/g, respectively. The results of adsorption isotherm models also showed that the use of the linear form could lead to a completely different interpretation, as compared to the original form of the model. Based on the linear forms, the Langmuir isotherm was the best; meanwhile, according to the non-linear forms, the Freundlich isotherm was the best model to describe the adsorption data. In addition, the reaction kinetics indicated that both original and linear models had the same results, and the data were better fitted by the pseudo-second order model.

The water footprint is an analytical tool that offers a better and more comprehensive view of how consumers or producers engage with freshwater consumption. Given the water crisis in the country, particularly in Isfahan Province, this study aims to estimate and compare the direct and indirect water footprints of several large industries, including Mobarakeh Steel, Iron Smelting, Refinery, and Power Plant, located in the Zayandeh River Basin. After identifying the desired objectives and study areas, as well as confirming the availability of the required data, information was gathered from the selected industries. Two methods were then utilized to aggregate the entire chain and the sum of steps to calculate the water footprint in the researched industries. According to the calculations, the direct and indirect water footprint in the iron smelting industry amounts to 196.9 cubic meters per ton of steel annually, of which 4.026 cubic meters is attributed to direct consumption and 17.5 cubic meters to indirect consumption. In a refinery, 18.80 liters of water are consumed directly and indirectly to produce one barrel of product (gasoline or diesel). Additionally, the direct and indirect water footprint of the Islamabad power plant is 1,198,320 cubic meters per terajoule, equating to 4.31 liters per kilowatt hour. The results of this study indicate that the indirect water footprint in the analyzed industries is equal to or exceeds direct water consumption, with both being equally significant. Finally, it is important to note that the results of this study can support decision-makers and policymakers in the industry, including those in the iron and steel, refinery, and power plant sectors, in managing their water footprint.