Optimization and Characterization of Tl(I) Adsorption onto Modified Ulmus carpinifolia Tree Leaves

Abstract

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 ...

Cercis siliquastrum Tree Leaves as an Efficient Adsorbent for Removal of Ag(I): Response Surface Optimization and Characterization of Biosorption

“…There are only a few reports for removal of Ag(I) by biosorbents, particularly by tree leaves such as Cercis siliquastrum [1,8,10,11]. Some variables such as pH, sorbent amount, sorbate concentration, shaking time, and temperature are likely to have significant simultaneous influence on biosorption efficiency [15][16][17][18][19][20]. Therefore, the optimization of biosorption process is crucial and should be ascertained.…”

“…The lack of systematic multivariate optimization of Ag(I) biosorption in the literature has drawn more attention on this particular aspect of biochemical process [1,10]. The multivariate optimization has several advantages over conventional ''one-at-atime'' method because of providing more information through running fewer experiments [15][16][17][18][19][20][21][22][23][24]. During multivariate optimization, a response surface methodology (RSM) leads to an empirical mathematical model, which relates the removal percent of metal ion with effective variables and their interactions [17][18][19][21][22][23][24].…”

“…Apart from the agricultural residue, use of tree leaves as a sorbent, which are cheap and easily available in great supply, has been of greatest interest to researchers in recent years [11][12][13][14]. Many of tree leaves have recently been used by our research group for instance, Ulmus carpinifolia, Fraxinus excelsior, Robinia, Elaeagnus, Fraxinus, and Platanus for removing Cu(II), Tl(I), Cd(II), Pb(II), Cr(VI), Hg(II), and methylene blue, respectively, from aqueous solution [14][15][16][17][18][19][20]. There are only a few reports for removal of Ag(I) by biosorbents, particularly by tree leaves such as Cercis siliquastrum [1,8,10,11].…”

“…For this purpose the central composite design (CCD) as a response surface approach is developed for finding out the optimum conditions and maximum removal of Ag(I) from aqueous solution [15,18,19]. Apart from that, the determination of proton binding active sites at different pHs on the biosorbent along with recognition of the mechanism of Ag(I) removal from aqueous solutions using Cercis siliquastrum tree leaves as a biosorbent are pursued [25][26][27].…”

Multi-templated Pb-Zn-Hg Ion Imprinted Polymer for the Selective and Simultaneous Removal of Toxic Metallic Ions from Wastewater

“…Then 25 ml of the 5 mg/l standard mixture solution at pH 7.5 was added into each flask (Zolgharnein et al 2011). The mixture was shaken for optimum time (15 min), filtered with Whatman 45 mm Ø filter paper and analyzed with AAS.…”