In present work, a graphene oxide chemically modified with 2,2'-dipyridylamine (GO-DPA), was synthesized by simple, fast and low-cost process for the simultaneous adsorption of four toxic heavy metals, Pb(II), Cd(II), Ni(II) and Cu(II), from aqueous solutions. The synthesized adsorbent was characterized by FT-IR, XRD, XPS, SEM and AFM measurements. The effects of variables such as pH solution, initial ion concentrations, adsorbent dosage and sonicating time were investigated on adsorption efficiency by rotatable central composite design. The optimum conditions, specified as 8mg of adsorbent, 20mgL(-1) of each ion at pH 5 and short time of 4min led to the achievement of a high adsorption capacities. Ultrasonic power had important role in shortening the adsorption time of ions by enhancing the dispersion of adsorbent in solution. The adsorption kinetic studies and equilibrium isotherms for evaluating the mechanism of adsorption process showed a good fit to the pseudo-second order and Langmuir model, respectively. The maximum adsorption capacities (Qm) of this adsorbent were 369.749, 257.201, 180.893 and 358.824mgg(-1) for lead, cadmium, nickel and copper ions, respectively. The removal performance of adsorbent on the real wastewater samples also showed the feasibility of adsorbent for applying in industrial purposes.

In the present work, metal organic framework MIL-68 (MIL = Material of Institute Lavoisier), with metal sites of aluminum ions (namely MIL-68(Al)), was synthesized by a simple, fast and low-cost process for simultaneous removal of Methylene Blue (MB) and Rhodamine B (RhB), regarded to be toxic and even carcinogenic, from aqueous solution. The adsorbent was characterized by FTIR, SEM, XRD, BET and TG analysis. Optimization of significant variables such as pH, adsorbent dosage, initial MB concentration, initial RhB concentration and adsorption time affecting both single and binary dye removal was developed by Central Composite Design (CCD) under response surface methodology (RSM), and the optimized values for these parameters in binary solutions were found to be 6.45, 0.014 g, 60 mg L⁻¹, 15 mg L⁻¹ and 9.9 min, respectively. The kinetics and isotherm of the adsorption were investigated in detail. Maximum sorption capacities of 1666, 1111, 227 and 29 mg g⁻¹ were obtained from the Langmuir isotherms for MB and RhB in single and binary solutions, respectively. The kinetics study results suggested that the sorption of the studied dyes onto MIL-68(Al) follows the pseudo-second order model. According to the reusability test of the adsorbent, dye uploaded MIL-68(Al) can be regenerated using methanol. The regenerated sorbent was used for three cycles use with high performance. The effect of ionic strength on the removal efficiency of the sorbent was also tested with different kinds of salts. The applicability of the sorbent was examined for real samples spiked with specific quantities of both dyes in water from tap water, sea water, spring water and laundry wastewater. The short time required for dye uptake makes this MOF a promising sorbent for simultaneous and rapid removal of dyes even in the real polluted environment.

A novel adsorbent, based on modifying graphene oxide (GO) chemically with 2-pyridinecarboxaldehyde thiosemicarbazone (2-PTSC) as ligand, was designed by facile process for removal of Hg(II) from aqueous solution. Characterization of the adsorbent was performed using various techniques, such as FT-IR, XRD, XPS, SEM and AFM analysis. The adsorption capacity was affected by variables such as adsorbent dosage, pH solution, Hg(2+) initial concentration and sonicating time. These variables were optimized by rotatable central composite design (CCD) under response surface methodology (RSM). The predictive model for Hg(II) adsorption was constructed and applied to find the best conditions at which the responses were maximized. In this conditions, the adsorption capacity of this adsorbent for Hg(2+) ions was calculated to be 309mgg(-1) that was higher than that of GO. Appling the ultrasound power combined with adsorption method was very efficient in shortening the removal time of Hg(2+) ions by enhancing the dispersion of adsorbent and metal ions in solution and effective interactions among them. The adsorption process was well described by second-order kinetic and Langmuir isotherm model in which the maximum adsorption capacity (Qm) was found to be 555mgg(-1) for adsorption of Hg(2+) ions over the obtained adsorbent. The performance of adsorbent was examined on the real wastewaters and confirmed the applicability of adsorbent for practical applications.