Mohammad Khazaei

Selective removal of lead ions from aqueous solutions using 1,8-dihydroxyanthraquinone (DHAQ) functionalized graphene oxide; isotherm, kinetic and thermodynamic studies

An anthraquinone – graphene structure was fabricated and applied for the removal of lead(II) from aqueous solution. The equilibrium occurred in about 10 min revealing the high adsorption rate at the beginning of the process. The maximum Pb(II) adsorption capacity of the Fe3O4@DHAQ_GO nanocomposite was about 283.5 mg g−1 that was observed at 323 K and pH 5.5. The Pb(II) adsorption ability increased with the increasing pH. The isotherm and kinetic studies indicated that the Sips isotherm model and the linear form of the pseudo-second kinetic model had a better fit with the experimental results. The positive value of ΔH0 indicated endothermic interactions between Pb(II) and Fe3O4@DHAQ_GO. The negative ΔG0 indicated that the reactions are spontaneous with a high affinity for Pb(II). The positive ΔS0 values indicated increasing randomness at the solid–solute interface during the adsorption process. The selective removal of Pb(II) by the nanocomposite confirms the presence of higher-affinity binding sites for Pb(II) than Cd(II), Co(II), Zn(II), and Ni(II) ions. Furthermore, the Fe3O4@DHAQ_GO nanocomposite revealed an excellent preferential adsorbent for Pb(II) spiked in drinking water samples containing natural ion matrices. EDTA-2NA 0.01 N was found to be a better elution agent than HCl 0.1 M for the nanocomposite regeneration. After five adsorption/desorption cycles using EDTA-2NA 0.01 N, more than 84% of the adsorbed Pb(II) was still desorbed in 30 min. Capturing sub-ppm initial concentrations of Pb(II) and the capability to selectively remove lead from drinking water samples make the Fe3O4@DHAQ_GO nanocomposite practically convenient for water treatment purposes. High adsorption capacity and facile chemical synthesis route are the other advancements.

Hexavalent chromium removal from aqueous solution using functionalized chitosan as a novel nano-adsorbent: modeling and optimization, kinetic, isotherm, and thermodynamic studies, and toxicity testing

Hexavalent chromium is a highly toxic metal that can enter drinking water sources. Chitosan, which contains amino and hydroxyl functional groups, is considered an appropriate candidate to remove heavy metals through absorption. In this study, a novel adsorbent, magnetic nanoparticles of chitosan modified with polyhexamethylene biguanide (Ch-PHMB NPs) was synthesized and was used to successfully remove chromium from aqueous solution. Quadratic models with independent variables including pH, adsorbent dosage, time, and the initial concentration of chromium were proposed through RSM to describe the behavior of both magnetic chitosan (M-Ch) and Ch-PHMB NPs in Cr(VI) removal. Optimized models with adjusted R2 values of 0.8326 and 0.74 for M-Ch and Ch-PHMB NPs were developed. Cr(VI) removal from aqueous solution by both absorbents followed pseudo-second-order kinetics. The experimental data were best fitted to the Temkin and Freundlich models for M-Ch and Ch-PHMB NPs, respectively. M-Ch and Ch-PHMB NPs can effectively remove the hexavalent chromium from aqueous solution with pH above 7. Ch-PHMB NPs have higher removal efficiency than M-Ch, removing up to 70% of Cr(VI) from aqueous solution. However, toxicity evaluation on Daphnia magna revealed that Ch-PHMB NPs was more toxic than M-Ch nanoparticles.

Trends of metals enrichment in deposited particulate matter at semi-arid area of Iran

The presence and enrichment of heavy metals in dust depositions have been recognized as an emerging environmental health issues in the urban and industrial areas. In this study, the deposition of some metals was found in Qom, a city located in a semi-desert area in Iran that is surrounded by industrial areas. Dust deposition samples were collected using five sampling stations during a year. Dust samples were digested applying acidic condition and then, the metal content was analyzed using inductively coupled plasma technology (ICP-OES). Comparative results showed the following order, from the maximum to the minimum concentration (mg/kg dust) of elements: Ca > Al > Fe > Mg > Ti > Si > K > B > Sr > Mn > P > Ba > Cr > Zn > Ni > Sn > Pb > V > Na > Cu > Co > U > Li > Ce > Ag. The differences among the average concentrations of metals in the five stations were not significant (p value > 0.05). The average concentration of some metals increased significantly during cold seasons. In this study, the cluster analysis (CA) and princicipal component analysis (PCA) were applied, and relationships among some elements in different clusters were found. In addition, the geo-accumulation and enrichment analysis revealed that the following metals had been enriched more than the average values: boron, silver, tin, uranium, lead, zinc, cobalt, chromium, lithium, nickel, strontium, and coper. The presence of thermal power plant, pesticide manufacturing plants, publishing centers, traffic jam, and some industrial areas around the city has resulted in the enrichment of some metals (particularly in cold seasons with atmospheric stable conditions) in dust deposition.

Survey of performance microbial fuel cell for wastewater treatment and electricity generation

Background and objective: Microbial fuel cell (MFC) is a bio electrochemical system and a new method for wastewater treatment and electricity generation simultaneously. In this reactor chemical energy stored in organic materials convert to electricity through the metabolic activity of the microorganisms. Material & Methods: In a pilot study, two chambers MFC operated in continuous mode during 720 hours at 20±40C. Organic loading rate and hydraulic retention time (HRT) were effective variables for operation of reactor. Results: Optimized HRT to achieve the maximum removal efficiency obtained 1.5 and 2.5 hours and reached to 49%. Results showed that Columbic efficiency affected by organic loading rate (OLR) and by increasing it, CE reduced from 71% to 8%. Conclusion: By considering, advantages such as production electricity directly and wastewater treatment simultaneously, it is recommended after further complementary studies and economical assessment, MFC could be used for wastewater treatment in industrial level.