A dependency of the R% and the maximum capacity of sorbent (qmax) was verified. Experimental MaterialsPlatanus tree leaves were collected from a grove in a suburb 2010

Optimization and Characterization of Tl(I) Adsorption onto Modified Ulmus carpinifolia Tree LeavesUlmus carpinifolia tree leaves were successfully used to remove Tl(I) from aqueous solution in a batch system. In order to improve the uptake capacity of sorbent, it was modified by various chemical agents such as NaOH, HNO 3 , NH 3 , NaCl, NaHCO 3 , and CaCl 2 . Among the modifiers, NaCl was the best. Equilibrium behavior of sorbent with Tl(I) was examined by the several isotherms. Considering modified U. carpinifolia equilibrium data fitted well to the Langmuir model with maximum capacity of 54.6 mg/g. The other isotherms such as: Freundlich and Dubinin-Redushkevich (D-R) models were also examined. The central composite design (CCD) was successfully employed for optimization of biosorption process. An empirical model was given through using response surface methodology. Also its validation was recognized by using relevant statistical tests such as ANOVA. The optimum conditions of biosorption: pH, m (amount of sorbent) and C (initial concentration) were found to be 7.9, 11.4 g/L, and 8.8 mg/L, respectively. On the other hand thermodynamic parameters: DG, DH, and DS were evaluated: the obtained results show that biosorption process was spontaneous and exothermic. Eventually, FT-IR analysis confirmed that the main functional groups of sorbent have been involved through the biosorption process. IntroductionThe presence of heavy metals in the environment poses a problem due to their harmful affects on human health and biota. Thallium is a heavy metallic element that exists in the environment mainly combined with other elements (primarily oxygen, sulfur, and halogen) [1]. Thallium (Tl) is considered as a non-essential and highly toxic element, which is produced as a by-product in the refining of iron, cadmium, and zinc [2,3]. It is used as a catalyst in certain alloys, optical lenses, jewels, low-temperature thermometers, semiconductors, metal mining, ore processing and combustion of coal [1,2]. Thallium is more toxic to humans than mercury, cadmium, lead, copper, or zinc and has been responsible for many accidental, occupational, deliberate, and therapeutic poisonings since its discovery in 1861 [4]. It occurs almost exclusively in natural waters as monovalent thallous cation. The solubility of thallous compounds is relatively high so that monovalent thallium is readily transported through aqueous routes into the environment. The fascinating chemistry and high toxicity potential make thallium and its compounds of particular scientific interest and environmental concern [4]. Thallium is present mainly in industrial wastewaters [5]. Due to these adverse biological and environmental effects, it is required to have some improved methods for detecting, monitoring, and removing it from environmental sources and industrial waste effluents. The conventional waste water treatments which used for removal of heavy metal ions are including: Chemical precipitation, ion exchange, and membrane technologies, adsorption onto activated ...

Ulmus tree leaves were successfully used as a novel and efficient biosorbent for removing cadmium, (Cd(II)), from aqueous solutions in a batch system. A multivariate strategy for optimization of removal efficiency conditions of Cd(II) was carried out. A 2 3 full factorial design with three center points (9 runs) was performed for screening the main variables and reducing the large number of experimental runs. Initial concentration of metal ion (C m ), amount of sorbent (m), and pH were considered as the three main variables at two different levels. The maximum removal efficiency of Cd(II) was achieved within 1 h contact time. It was found that all the main factors and their interactions were significant at p 5 0.05. Doehlert response surface methodology was utilized (13 runs) for finding a suitable mathematical model. The analysis of variance and some statistical tests such as lack-of-fit, coefficient of determination (R 2 ), and residual distribution plot confirmed the validity of the model. The optimum conditions for maximum removal of Cd(II) by Ulmus tree leaves were found as pH ¼ 3.4, m (amount of sorbent) ¼ 0.128 g, C m (initial concentration of metal ion) ¼ 12.1 mg L À1 .

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