In this research, the adsorption of nickel ions in the batch system by orange peel carbon has been investigated and the effect of factors such as pH, contact time, initial concentration of nickel in solution, adsorbent amount, and the temperature has been considered. The surface details and functional groups were investigated by SEM and FTIR analyzes, respectively. In the study of the effect of pH, the highest percentage of nickel uptake for orange peel carbon occurred at pH = 6, which is equivalent to 58 mg/g. With increasing the contact time between the adsorbent and the solution and after 210 minutes, the adsorption percentage increased to 98.57%. In the study of the effect of the initial concentration of nickel in the range of 20 to  150 mg/L, the results showed that with increasing concentration, the percentage of adsorption decreased from 98% to 96%, and with increasing the amount of adsorbent from 0.01 to 0.1 g per 25 ml. Nickel solution, the adsorption percentage increased from 90% to 98%. The effect of temperature showed that with increasing the temperature from 25 to 45°C, the percentage of adsorption decreased from 99% to 97.8%. Thermodynamic properties were studied at three temperatures of 25, 35, and 45°C. The negative free energy value of the standard Gibbs (∆ Go) which is equivalent to -121.3 kJ / mol, indicates that the adsorption process is spontaneous and physical. In the kinetic study of the contact time effect, it was observed that the results fit well with the second-order kinetic model with a correlation coefficient of 99%. In investigating the effect of the initial concentration of nickel in solution and fitting experimental data with Langmuir, Freundlich, Temkin, Dubin Radushkovich isotherms, and according to the values ​​obtained at R2, Freundlich's isotherm had the highest compatibility with 100% correlation coefficient.

In this research, the adsorption of Mg (II) was studied in a batch system by using zeolite, and the influence of effective parameters on the adsorption, such as initial pH, adsorbent dosage, contact time, initial Mg (II) concentration and temperature were investigated. Also, the surface characteristics and structure of the adsorbents were respectively obtained by SEM and FT-IR. The pH experimental results showed that the maximum adsorption efficiency of Mg (II) ion occurs at pH=7. By increasing the contact time between the adsorbent and solution, adsorption efficiency was raised, and after 60 minutes, equilibrium is reached. Results showed the adsorption efficiency decreased by increasing the initial concentrations of Mg (II) in the range of 50-250 ppm in solution, and the effect of adsorbent dosage showed that adsorption efficiency increased by increasing the adsorbent dosage from 0. 5g to 2. 5g. In addition, the higher adsorption of Mg (II) was observed at higher temperatures, which proves the endothermic behavior of the adsorption process. Thermodynamic parameters were investigated in three temperatures 25, 35, and, 45°, Ϲ, . The negative value of the Gibbs free energy (Δ, G˚, ) showed that the adsorption process was spontaneous. Positive value enthalpy (Δ, H˚, ) indicated that the adsorption process was endothermic, and positive value entropy (Δ, S˚, ) can be attributed to the increased randomness at the interface of the adsorbent and the solution. The experimental results for the effect of exposure time were examined for the kinetic study with three different models: Pseudo-First order, Pseudo-Second order, and Intra-Particle diffusion. Among these models, the best fit was observed for pseudo-second-order. The study for initial concentration of Mg (II) in the solution was studied by Langmuir, Freundlich, Temkin, and Dubnin-Radushkevich isotherms, and the best fit for the adsorbent was observed by Langmuir isotherm and the Langmuir maximum sorption capacity was found to be 4. 77 mg/g at 45°, C.

This paper assesses the use of certified Iraqi montmorillonite clay as a potential sorbent for the removal of oxytetracycline (OTC) from aqueous solutions. The clay is characterized by a cation exchange capacity of 0.756 meq.g-1 and a zero point charge at pH 8.7. Aqueous solutions of OTC were equilibrated with montmorillonite under various experimental conditions, such as OTC concentration, pH and clay content, for 24 h at fixed ionic strength. Two forms of montmorillonite were evaluated: regular, and iron-modified form. The effect of pH was minor on OTC adsorption. Kinetic study revealed that the sorption follows a pseudo second order model. Sorption isotherm showed a good fit with the Fruendlich model. OTC sorption onto Fe-saturated montmorillonite was analyzed statistically using a response surface design to study the effects of experimental conditions. The introduction of iron improved the adsorption characteristics of the clay due to the ability of ferric ions to make stable complexes with OTC. The most favorable operating conditions for the treatment were deemed as follows: clay content, 6.85 g.L-1, oxytetracycline concentration, 1.0 mmol.L-1 and pH, 5.5 for the iron modified form.

Iron oxide nanoparticles (nano-Fe) have been widely used in environmental remediation, including that of emerging contaminants, such as antibiotics. Magnetite nanoparticles (nano-Fe3O4) have been reported to form on the outer surface of nano-Fe and have the potential to be a good sorbent for certain antibiotics. This study reports, for the first time, the kinetics and thermodynamics of adsorption of a common tetracycline group antibiotic, oxytetracycline (OTC), on nano-Fe3O4. Batch sorption kinetics were evaluated by varying initial OTC concentration (0.25-2 mM), nano-Fe3O4 concentration (2.5-20 g L-1), pH (3.8-7.6), temperature (5, 15, 35 oC), and ionic strength (0.01-0.5 M KCl) to derive thermodynamic and kinetic constants. Results show that OTC sorption kinetics is rapid and increases with increasing temperature. The derived thermodynamic constants suggest a surface chemical-controlled reaction that proceeds via an associative mechanism. Results indicate the potential of developing a nano-magnetite-based remediation system for tetracycline group of antibiotics.

Gaz-angubin is a sweet exudate naturally produced by an insect from the Gavan-e-Gaz-angubin plant. Adsorption and desorption isotherms for a Gaz-angubin sample were determined at 15o and 25oC over a range of relative humidity from 0 to 90% using a dynamic vapor sorption system. At different levels of relative humidity, changes in sample mass were continuously measured versus time and described using an exponential model. Gaz-angubin exhibited type III sorption behavior. The sorption capacity decreased with increasing temperature. The sorption-desorption isotherms revealed the phenomenon of hysteresis, in which the equilibrium moisture content was higher at a particular equilibrium relative humidity for the desorption curve than for the adsorption curve. Water sorption/desorption isotherms were modelled using the Guggenheim-Anderson-de Boer (GAB) model. The GAB model showed a good fit to experimental data for water activities of up to about 0.75. It was observed that, for short intervals, the diffusion of water can be described by Fickian laws and Gaz-angubin showed essentially a Fickian diffusion.

The potential of activated carbon (a product of Merck) as an adsorbent has been studied for removal of nitrate from some polluted water sources. In line with this purpose, nitrate sorption kinetics and isotherms, as well as the effects of contact time, initial concentration, pH and temperature on nitrate sorption onto activated carbon were investigated. The surface characteristics of activated carbon were also studied, through FTIR and SEM techniques. Two simplified kinetics models, namely: pseudo-first and pseudo-second orders were tested to investigate the sorption mechanisms and while two isotherm models namely Freundlich and Langmuir employed to describe the equilibrium sorption of nitrate onto activated carbon. The results revealed that the amount of nitrate sorption increased with time and reached its maximum after ten minutes past. Maximum nitrate sorption occurred in a neutral pH figure, and with either increase or decrease in the pH level, the amount of sorption being decreased. The amount of nitrate sorption increased with a decrease in temperature, level, the depicting the exothermic nature of sorption. A comparison of the coefficient of determination of the fitted equations indicated that pseudo-second order equation (R2=1.000) was better fitting than pseudo-first order equation (R2=0.839) for description of nitrate sorption data. Sorption isotherm was proper, as described by Langmuier model (R2=0.998) and the maximum sorption parameter equaled 8.93 mg per gr of activated carbon.

In this paper a chemical method applied to synthesize exfoliated graphite (EG) is presented. In this method graphite intercalation compound (GIC) was firstly synthesized by chemical treatment of graphite flakes using a mixture of sulfuric and nitric acids followed by thermal shock of GIC at 1000°C to produce EG. The bulk density of synthesized EG was found to be as low as 4.5 kg/m3. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used for identification and characterization of different materials. According to the XRD observations, the GIC was identified as graphite bisulfate with stage 2, and residue GIC and EG had nearly the same diffraction pattern, but with distinctly lower intensity. In accordance with SEM results the residue graphite bisulfate was swelled in comparison with the graphite flake. The oil sorption capacity of synthesized EG in this work was studied by common static and dynamic tests and compared with other sorbents. The results show the superior capability of EG for oil spill cleanup.

We utilize isotherm models in contributing to scholarly knowledge in simple terms, to measure the forces or energy defining certain adsorption phenomenon. Gas Chromatography coupled with Mass Spectrophotometer detector (GCMS) was utilized to measure equilibrium phase atrazine after adsorption onto Shea nut Shells (SS) acid derived activated carbon. Data were fitted into the D-R and Temkin isotherm relationships for energy data estimation of Sorption energy value (BD), mean free energy (ED) and heat of sorption (B). They were estimated as 0.7600mol2KJ-2, 0.8111 kjmol-1 and 0.790Jmol-1 respectively. The parameter predicting the type of adsorption was evaluated BD, B<20kJ/mol and ED<8 which is an indication that physisorption (Non specific adsorption) dominates chemisorption and ion exchange. The D-R model with a higher correlation coefficient values, R2=0.979 proves a better choice in explaining sorption energies. Generally, shea nut shells can be used as alternative precursors for activated carbon production via the two steps and acid treatment method.

Soil adsorbing properties reduce sorption ability of the metal, which in turn may influence decision for remediation at contaminated sites. The objective of this study is presentation of a model based on soil properties to estimate the sorption of Cr(III) in chromium contaminated soils. Twenty uncontaminated soil samples, with properties similar to the contaminated soils were selected from around of city of Tabriz and treated with Cr as CrCl3. A multiple regression analysis with statgraph software was used to drive an expression that related Cr sorption to common soil properties. The results showed that four soil properties were important in determining the amount of Cr adsorbed by the soils including pH, cation exchange capacity, total inorganic carbon and clay content with nearly 80% variability in Cr sorption and a reasonable level of confidence by this model. The obtained model suggested that Cr(III) sorption was enhanced by higher soil pH, more total inorganic carbon, more clay, and higher cation exchange capacity.