Increasing concentrations of NO 3 − in surface water and groundwater can cause ecological and public health effects and has come under increased scrutiny by both environmental scientists and regulatory agencies. For many regions though, including the Sahel of Tunisia, little is known about the NO 3 − sorption capacity of soils. In this project we measured NO 3 − sorption by a profile of an isohumic soil from Chott Meriem, Tunisia. Soil samples were collected from four soil depths (0-25, 25-60, 60-90, and 90-120 cm) on 1 June 2011, and their sorption capacity was determined using batch experiments under laboratory conditions. The effects of contact time, the initial concentration, and the soil-solution ratio on NO 3 − sorption were investigated. In general, the results suggested that NO 3 − was weakly retained by the Chott Meriem soil profile. The quantity of NO 3 − sorption increased with depth, contact time, initial concentration, and soil-solution ratios. To evaluate the sorption capacities of the soil samples at concentrations ranging between 25 and 150 mg L −1 experimental data were fitted to both Freundlich and Langmuir isotherm sorption models. The results indicated that Freundlich model was better for describing NO 3 − sorption in this soil profile.
Many previous studies have been conducted in an attempt to determine phosphorus (P) adsorption in soil. Often, these studies cannot be compared, because the reports did not give a satisfactory characterization of the dynamics of soil P in saline conditions. In our experiment, three salts extracts (CaCl 2 , NaCl and KCl) with the same concentration (0.01 M) were used to determine the amount of P adsorption in Solonetz soil samples of the semi-arid areas of Kondar region (Tunisia). Also, we focused on the influence of contact time on P-Salts adsorption in the alkalize soil. The analytic data were approached from the following kinetics' models: pseudo first order, pseudo second order and Elovich model. Results obtained showed that salts addition increased significantly the amount of P adsorption with the following order of salts extracts (PCaCl 2 [ P-NaCl [ P-KCl [ P). The mechanism of phosphate ions adsorption by soil was studied using IR spectroscopy. Infrared spectral characteristics of the amorphous material indicated that the adsorption is due to exchange phenomena of phosphate ions with surface groups. It was also demonstrated that the addition of CaCl 2 salt caused a shift and an increase of OH, Si-O (Si-O-Si, Si-O-Al) and Al-OH absorption bands which favored the adsorption of P ions. Moreover, the second-order model was shown to be the best fit for describing phosphorus adsorption associated with different salts, as seen from the correlation coefficient R2 which ranged from 0.98 to 0.99.
An experiment was conducted at the experimental station of Higher Institute of Agronomy, Chott Mariem, Sousse (Tunisia) to investigate the effect of similar levels of nitrogen and potassium on potato growth (Spunta variety). Four similar levels of nitrogen (N) and potassium (K) (0, 50, 80 and 120 kg ha -1 ) were randomized complete block design with four replications. Data collected on growth and yield parameters were analyzed using SPSS.20 computer software. Nitrogen (N) and potassium (K) levels showed significant effect on mostly growth and yield parameters. It can be show that N and K application at the level of 120 kg ha -1 significantly affected plant height (59.16 cm), number of leaves plant -1 (294), number of branches plant -1 (14.66), fruits plant -1 (20.96), and leaf area (422.66) index. Additionally the maximum of dry matter (13.83%), tuber size (79 mm), tuber yield (22.193) and tuber weight (203.66 g) were recorded with 120 kg ha -1. From this study, it can be concluded that the higher levels of nitrogen (N) and potassium (K) (120 kgha -1) can be used for optimum production of potato variety Spunta in the study area.
The present study evaluates the phosphorus (P) adsorption by alkaline soil in fixed bed column mode operation. The effects of flow rate, bed height, and initial P concentration on breakthrough curves were evaluated. Data confirmed that both the breakthrough and exhaustion time increased in parallel with the rise in bed height and the decline in flow rate and initial P concentration. The adsorption capacity was observed to increase with decreasing flow rate and bed height and increasing initial concentration. Moreover, continuous adsorption experiments were conducted using three salts (NaCl, KCl and CaCl2) with the same concentration (0.01 M) to investigate the P adsorption behavior in saline conditions. The results showed that all three salts improve the P adsorption in the soil column. Consequently, the bed performance was significantly enhanced with salts addition. The maximum adsorption capacity of 13.47 mg g−1 for P, 16.13 mg g−1 for P-NaCl, 22.10 mg g−1 for P-KCl, 30.05 mg g−1 for P-CaCl2 was attained at an initial influent concentration of 300 mg g−1, bed height of 22 cm, and flow rate of 10 mL min−1. TheCaCl2 addition was therefore the most effective in increasing P adsorption. Thomas, Yoon-Nelson and Clark models were applied to experimental results to forecast the breakthrough curves by nonlinear regression analysis. Meanwhile, the bed depth service time model was employed to examine the effective model parameters in scaling up the process using linear regression analysis. The values of correlation coefficient (R2) and the sum of squared error evidenced that the Thomas model is the most appropriate model to fit the experimental data. The reusability experiment showed that the adsorbent material still had high P adsorption capacity, and tolerable desorption efficiency.
Organoclay has a tremendous impact on both fundamental studies and practical applications in numerous fields. In this context, this chapter investigates the performance of Organoclay in wastewater treatment. In particular, the adsorption of various hazardous substances has been reviewed. This study aims to give an overview of the preparation methods of Organoclay. The second purpose was to discuss the removal efficiency and reliability of various pollutants by organoclay. The third goal discussed the isotherms and kinetics used for the data interpretation. This work revealed that the characteristics of Organoclay depend mainly on the type of clay used and the nature of the intercalated surfactant. Sorption efficiency was found to depend on the nature of Organoclay, type of pollutant, pH, contact time and the concentration of pollutant.
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