دانلود رایگان ترجمه مقاله بررسی حذف سرب از فاضلاب صنعتی با جذب آن به بنتونیت خام و اصلاح شده (نشریه تیلور و فرانسیس ۲۰۱۳)

یک مطالعه مقایسه ای در مورد حذف سرب از پساب های صنعتی با استفاده از جذب آنها بر روی بنتونیت خام و اصلاح شده ایران (از منطقه اصفهان)

A comparative study on the removal of lead from industrial wastewater by adsorption onto raw and modified Iranian Bentonite (from Isfahan area)

Abstract

In recent years, Bentonite has attracted a lot of interest due to its potential applications and capability for removing heavy metals from aqueous solutions. This ability related to the high ionic exchange capacity and specific surface area. In this study, Iranian Bentonite obtained from Isfahan area was characterized by using X-ray diffraction, X-ray fluorescence, and IR spectroscopy. The effects of different parameters have been investigated on the adsorption of lead from aqueous solution such as contact time, metal concentrations, pH of solution, stirring speed, particle size, amount of Bentonite, and solid in comparison with liquid solution. Bentonite has been modified by NaCl and NH4Cl. As the equilibrium study and the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) models have been used and examined. The correlation coefficients (r 2 ) of lead adsorption have been increased by modification of Bentonite for all models. In addition, the Langmuir model is the best one with correlation coefficient (r 2 ) more than 0.995 for description/adsorption process of lead, which is applied on raw Bentonite and modified Bentonite. The correspondence of Langmuir model for maximum adsorption capacity of raw Bentonite, NaCl–Bentonite, and NH4Cl–Bentonite is 79.3, 102.0, and 94.3 mg/g, respectively.

۱ Introduction

Releasing of lead into the environment has detrimental effects on health. Unfortunately, there is a high risk of undesirable exposure and spread of this pollutant in the environment. It could be discharged into air, water, and soil by many industrial activities such as mining operation, manufacture of storage batteries, painting pigments, petroleum refining, automobiles, and cable covering. Toxicity of lead can cause various health conditions and diseases such as hypertension, nephritis, abdominal pain, constipation, cramps, nausea, vomiting, behavioral changes, learning disabilities, and cancers [1–۳]. These diseases caused by lead can be interfered in biological processes which are related to interaction of lead with functional groups of biological molecules.

There are many methods for removing heavy metals from aqueous solution such as ion exchange, solvent extraction, reverse osmosis, chemical precipitation, adsorption, and membrane processes [4–۶]. The adsorption method is one of the popular methods for removing of heavy metal from solution, which has been performed by two categories of synthesized and natural materials. The synthesized materials are active carbon [7], magnetic [8], zeolite [9], and natural minerals which contain mineral material, industrial, agricultural, and forest wastes. However, natural minerals such as Bentonite [10], Kolanite [11], and Zeolite [12] are widely applied in many fields of technology and science for removing heavy metals and organic pollutants from solution and gas.

Bentonite is volcanic clay. Montmorillonite is the main clay mineral constituent of Bentonite and belongs to Smectitic clay minerals with (Na, Ca)0.33 (Al, Mg)2Si4O10(OH)2·nH2O formula. Montmorillonite has layer structure with one octahedral coordinated layer of aluminum as the basic structural unit, which is sandwiched between two tetrahedral coordinated layers of silicon. The electrostatic interaction between these layers is a weak Van Der Waals force, which facilitates intercalation process. Net negative surface charge on the Bentonite due to the defect of crystal frame work that has been originated substitution of aluminum ion for silicon ion and magnesium or iron ions for aluminum in the tetrahedral sheets and octahedral sheets, respectively. The exchangeable cations such as H+ , Na+ , and Ca2+ on the layer surface are counterbalance charges of Bentonite [13].

In recent years, many papers have reported on the removal of heavy metal, dye, and other pollutants by using various types of Bentonite [13–۱۶]. In addition, the ability of adsorption of many metals such as Cd, Zn, Fe, Hg, Cr, Cu, Mn, and Pb onto Bentonite has been well recognized [16–۱۸].

The literature survey shows that Bentonite is one of the significant adsorbent to remove and to separate lead from solution, because it has high cation exchange capacity (90–۱۲۰ meq/g), high elasticity and plasticity, low cost, easy handling, abundance as an adsorbent, and easy refining [19]. In the last two decades, the removal of lead from wastewater has been studied considerably [20]. The removal of lead from aqueous solution with Bentonite has been reported since 1993 [21]. After this mentioned time, various types of raw and modified Bentonite have been used as adsorbent to remove lead [22–۲۶] (Table 1).

Bentonite has been modified by 8-hydroxy quinoline [27], sodium tetra borate [28], acid activated Bentonite (AAB) [29], sodium compounds [30], iron oxide and magnesium oxide [23], and 4-aminoantipyrine [18] for removing lead. The best result of lead adsorption is related to 8-hydroxy quinoline-immobilized Bentonite with the adsorption capacity of 142.9 mg/g of lead [27].

Although these mentioned reports covered the subject well, Iranian Bentonite has not yet been studied very well for removing heavy metal (particularly for removing lead from aqueous solution). In this study, the main factors involved in the adsorption process and the determination of optimum conditions for reaching the best adsorption efficiencies were attained. The main purpose of this study is to investigate utilization of Iranian Bentonite (Isfahan area) to remove lead from aqueous solution. The adsorption isotherms models as Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) have been investigated for lead adsorption process into Iranian Bentonite.