New group of polymers have been synthesized that are electricity conductive. Therefore, they are called conducting polymers. These so-called artificial metals have interesting optical and electrical properties. One of the most conductive polymers is "polyaniline" that is synthesized easily at low cost and with excellent environmental stability. Polyaniline is synthesized chemically and electrochemically in the shape of powder and film. The synthesis condition is noticeably effective on the properties of the produced polyaniline.Reaction temperature, molar ratio of aniline/oxidant, types and concentration of oxidant used in synthesis, will influence the morphology and conductivity of polyaniline. In this paper, Absorptive characteristics of polyaniline synthesized with two different oxidants including potassium iodate and ammonium persulfate has been studied.

In this study, a selective and sensitive ion-selective liquid membrane electrode based on 2-benzamidopropanoic acid to the determination of CHROMIUM (III) was prepared. This electrode exhibits a Nernstian response for CHROMIUM (III) ions over a concentration range (0. 3´ 10-1 to 1. 0´ 10-5 mol/L) with a slope of 22. 3 mV per decade. The limit of detection of the electrode was 8. 0×10-6 mol/L. The sensor has a relatively fast response time (<10 s) and a useful working pH range of 3. 5– 8. 0. Interference of some cations was also evaluated. The practical utility of the CHROMIUM (III) ion sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of CHROMIUM (III) with EDTA and for direct determination of CHROMIUM (III) in tea and cacao powder samples. Finally, the effect of ionic liquid of 1-Methyl-3-Pentylimidazolium bromide as an ionic additive was investigated.

Sorption of 3 poisonous metal ions (Pb2+, Cd2+, Cr3+) in aqueous solutions by two phosphate sorbents under dynamic and static conditions was studied. Phosphate sorbents (MgNH4PO4. H2O, Mg3(PO4)2. 6H2O) were synthesized by known procedures. The resulting crystalline samples were analyzed for the contents of Mg2+, Pb2+, P, N using spectrophotometric and elemental analysis methods. Likewise, the amounts of Pb2+, Cd2+, Cr3+ in solutions were determined before and after the sorption process using the atomic absorption method. The relative standard deviations for Pb2+, Cd2+, Cr3+ were 4.7%, 2.17%, and 1.61% and the detection limits were 5mg/L, 0.05 mg/L, and 0.1 mg/L, respectively. The sorbents showed a high performance in the purification of contaminated solutions under static conditions. The sorption capacity levels of Mg3 (PO4)2. 6H2O and MgNH4 PO4. H2O were 9.8m.mol/gr and 8.9m.mol/gr for Pb2+; 10.5m.mol/gr and 9m.mol/gr for Cd2+; and 6.6m.mol/gr and 5.3m.mol/gr for Cr3+, respectively. Pb2+ , Cd2+, Cr3+. sorption by inorganic phosphate sorbents from solutions is associated with complicated chemical transformations of the sorbents. A proper account of these transformations allows for the sorption process to be optimized. The data on Pb2+, Cd2+, Cr3+ sorption under static conditions (24-h contact of Mg3 (PO4)2. 6H2O, MgNH4PO4. H2O, with solutions at 20°C) and under dynamic conditions were obtained and the sorption behaviors of the metal ions were investigated in response to the sorbents used. It was found that Mg3 (PO4)2. 6H2O was the best sorbent for Pb2+, Cd2+, Cr3+ under dynamic conditions.

Background and Objective: Tannery industries effluent contain 100-1000 mg/L Cr+3 and due to changing to Cr+6 its direct disposal into environment is potentiqlly hazardous and threaten the health of humans through contaminating to the environment. In the recent years, many studies have been carried out concerning the removal of heavy metals from synthetic effluent using fungi and algae. The aim of this study as a basic and applied, investigation is to assess the possibility of the growth of Aspergillus niger in tannery effluent and its role in removal of CHROMIUM from these industrial wastes. Materials and Methods: Firstly the chemical quality of tannery effluent was assessed through measuring Cr+3 , total organic Carbon (TOC), total kadjeldal Nitrogen (TKN), Phosphate and pH (based on the latest standard methods for examinations of water and waste water). The ratio of carbon to nitrogen was adjusted to the optimal rate (C/N=10) prior to inoculation of 0.04-0.24% (dry weight) of A.niger into the effluent samples contained 122.5-1102.5mg/L of initial CHROMIUM. The samples were placed in a shaking incubator at 30°C, 150 rpm for 24 h. The rate of fungi biomass growth, the ratio of the grown fungi biomass to the CHROMIUM concentration and the percentage of CHROMIUM removal were then determined. Results: Findings of this experiment showed that the rate of fungi growth was increased in effluent that was initially contained 122.5 -1102.5 mg/L of Cr+3 . However, effluent containing more than 1102.5 mg/L was able to stop the fungi growth. The best values of CHROMIUM removal (93.4 % was observed at the initial concentration of 245mg/L (dry weight). Also the rate of biomass growth and the ratio of grown biomass to the CHROMIUM concentration were 0.4407 % and 18 mg/mg Cr+3  respectively. Conclusion: A.niger has an optimal growth in the tannery effluent at the CHROMIUM concentration of 122.5–245 mg/L. Analysis of variance showed that the initial concentration of CHROMIUM in effluent and/or the amount of inocalm have a significant effect on the rate of biomass growth and CHROMIUM removal efficiency (p>0.001).The CHROMIUM removal efficiency and the ratio of fungi biomass to CHROMIUM concentration decreases when the concentration of CHROMIUM is higher than 245mg/L.    

Natural processes and industrial activities can cause CHROMIUM to enter water resources. CHROMIUM in water enters food chain and causes diseases like cancer, skin dermatitis, and other health problems. In this work, cellulose adsorbent, Kraft paper, was used to remove CHROMIUM (VI) from water. The ash of the cellulose adsorbent was 2%, and its specific surface area was 3. 6 m2/g according to the BJH isotherm adsorption branch. Cellulose adsorbent was also characterized by FTIR, SEM, and EDX methods. The effects of pH were investigated in Cr(VI) adsorption and showed that with the increase in pH of the solution, Cr (VI) removal was decreased. The adsorption isotherm was corresponded to the Langmuir model. The kinetic data was in agreement with the pseudo first order model. The thermodynamic studies showed that Cr (VI) adsorption on the cellulose adsorbent was endothermic and spontaneous. The cellulose adsorbent, Kraft paper, in powder and sheet forms can remove Cr (VI) from water solutions. In the operating conditions of pH 2, powdery adsorbent dose 3 g in 50 mL of CHROMIUM solution with the concentration of 10 mg/L in 25 ° C after 2 h, 99. 16% CHROMIUM (VI) removal yield was obtained.

In order to investigate the influence of vermicompost (VC) on the concentration of nickel (Ni) and CHROMIUM (Cr) in soil and rice this research was conducted as a split plot based on randomized complete block design with three replications in 2008. Main factor (fertilizer) was added to soil in 6 levels, 20 and 40 ton ha-1 VC, 20 and 40 ton ha-1 VC enriched with 50% chemical fertilizer (CF), CF (based on soil testing comprise 100 kg. ha-1 urea, 150 kg. ha-1 triple super phosphate and 100 kg. ha-1 potassium sulphate) and control. Sub plot, were considered application periods that comprise 1, 2 and 3 years application. Results showed that the maximum available Ni (2.20 mg kg-1) belonged to 3 years application of 40 ton enriched VC. In 3 continuous years application of enriched 20 and 40 ton ha-1 measured the highest available Cr (0.109 mg kg-1). The highest concentration of Ni in root belong to 3 continuous years application of 40 ton VC +50% chemical fertilizer that was about 63% more than control treatment. With application of 40 ton VC per hectare during 2 and 3 years, measured the maximum Ni concentration in grain with about 2 times of control treatment. Also, the most content of Cr in root (8.43 mg kg-1) and grain (4.25 mg kg-1) belonged to 3 years application of enriched 40 and 20 ton ha-1, respectively.

Introduction: Hexavalent CHROMIUM (VI) is a very strong oxidizing agent that, despite its many uses in various industries, duration of the exposure can lead to lung cancer, deep wounds (in the hands, arm, tongue and palate), nasal septum perforation, burning and inflammation in the nose, lung and upper respiratory tract, asthma, contact dermatitis, damage to the kidneys and liver, and skin allergy. This study aimed to determine the activated carbon efficiency in CHROMIUM adsorption (VI) from air flow and its effective parameters.Material and Method: In this experimental study, CHROMIUM mists were generated by a nebulizer (3A model, Italy). Performance of activated carbon in the Cr (VI) adsorption and its influencing factors such as air flow rate (1 and 3L/min), the initial Cr concentration (0.05, 0.15, 1 and 10 mg/m3) and bed depth (2.5, 5 and 10 cm) were investigated. Yoon-Nelson and Thomas models were used to predict performance of adsorbent column and correlation test was used to determine accordance between the model and actual data.Result: Activated carbon adsorption capacity increased with increasing of bed depth but decreased with increasing of flow rate and inlet concentration. The results showed that the Yoon-Nelson and Thomas models with a correlation coefficient above 0.9953 matched with the experimental data.Conclusion: The results indicated that activated carbon has a high efficiency in Cr (VI) adsorption, so that its efficiency at flow rate of 3 L/m, depth of 5 cm and concentration of 20 TLV and TLV was 85.42 and 71.83 percent respectively.

The batch removal of Cr(VI) from aqueous solution using lignocellulosic solid wastes such as sawdust and pine leaves under different experimental conditions was investigated in this study. The influence of pH, temperature, contact time, initial concentration of Cr(VI) and particle size on the  CHROMIUM removal was investigated. Adsorption of Cr(VI) is highly pH-dependent and the results indicate that the optimum pH for the removal is 2. The capacity of CHROMIUM adsorption at equilibrium by these natural wastes increased with absorbent concentration. Temperature in the range of 20-60 °C showed a restricted effect on the adsorption capacity of pine leaves, but had a considerable effect on the adsorption capacity of sawdust. The capacity of CHROMIUM adsorption at the equilibrium increased with the decrease in particle sizes. The suitability of adsorbents was tested with Langmuir and Freundlich isotherms and their constants were evaluated. Results indicated that the Freundlich model gave a better fit to the experimental data in comparison with the Langmuir equation. The study showed that lignocellulosic solid wastes such as sawdust and pine leaves can be used as effective adsorbents for removal of Cr(VI) from wastewater.  

Metal biosorption on plant-based materials and agricultural wastes is a well practiced but a complex process affected by several factors. The biosorption of CHROMIUM(VI) from aqueous solution onto waste plant biomass of Portulaca Oleracea was studied in the present work. Batch studies were carried out to examine the effects of process parameters. Influence of altering various process parameters was studied. The biosorption process was fast, and equilibrium was achieved in 45 min of contact time. It was found that the biosorption capacity of plant material depends on many factors mainly on solution pH, with a maximum biosorption capacity for CHROMIUM at pH 2. The biosorption kinetics was tested with pseudo-first-order and pseudo-second-order reaction, and results showed that biosorption followed pseudo-second-order rate expression. Experimental equilibrium data were applied to two different isotherm models. Isotherm tests showed that equilibrium sorption data were better represented by Langmuir model, and the sorption capacity of plant biomass was found to be 54.945 mg/g. Thermodynamic parameters like DG 0, DH 0 and DS 0 were also evaluated, and it was found that the biosorption was spontaneous and endothermic in nature. Plant biomass was found to be an effective adsorbent for CHROMIUM (VI) from aqueous solution. This study indicated that plant biomass could be used as an efficient, cost-effective and environmentally safe biosorbent for the treatment of CHROMIUM containing aqueous solutions.

CHROMIUM is among the metals that, due to its particular specifications, has numerous applications in various fields of industries and its use in industry is steadily on the increas. Widspread use of this metal has been accompanied by its increased release into environment, entailing numerous environmental hazards. In this research the effect of organic adsorbents was investigated on hexavalent CHROMIUM adsorption from soils cotaminated through leather tanning industries. A factorial design with three replications was employed. Treatments consisted of three types of adsorbents (wool, sawdust and peat moss), three concentrations of adsorbents namely 2, 5 and 10%; along with three contact times of 2, 15 and 30 days. The results indicated that use of organic adsorbents is effective among them wool being the most suitable and the most applicable one. Different concentrations of adsorbents had different significant effects on CHROMIUM adsorption. Different application times also had different significant effects on CHROMIUM adsorption. Wool and sawdust had their maximum adsorption effect in 15 and 2 day, treatments respectively, but peat moss, adsorption of CHROMIUM contaminant was the same for the different application times.