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Removal of Cr(VI) ions from aqueous solution was investigated using activated carbon obtained from acid modified (AMCAC) and unmodified corncorb (UMCAC) by batch adsorption technique at 30°C. H2SO4 acid of 10N, 20N, and 30N concentrations were used for the modification of activated carbon. The effect of different adsorption parameters, such as pH, initial Cr(VI) ion concentration, contact time, and adsorbent dosage were studied. The 10N acid modified activated carbon (AMCAC) was effective for the maximum removal of Cr(VI) at pH 6.0, and equilibrium was attained in 60 min. Kinetic studies show that the pseudo‐second‐order kinetic equation was best suited for removal of Cr(IV) ions from aqueous solution. Adsorption equilibrium data were fitted to Langmuir, Freundlich, and Redlich‐Peterson adsorption isotherms. The maximum adsorption capacities of UMCAC and AMCAC with respect to Cr(VI) ions were calculated from Langmuir isotherm, and found to be 22.82, and 54.11 mg/g respectively. FTIR spectra of the adsorbent before and after adsorption with Cr(VI) indicated that hydroxyl, halide, and aldehyde groups are present in the major binding sites which play an important role in the removal of Cr(VI) ions. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 673–680, 2013

A low cost adsorbent prepared from material of biological origin Setaria verticillata (Grasses) has been utilized as an adsorbent for the removal of Reactive Yellow 15 (RY15) dye from an aqueous solution. The combined effect of the initial pH, adsorbent dose, and initial dye concentration was investigated using Response Surface Methodology (RSM). The most influential adsorption factor on each adsorption experimental design response was identified from the Analysis Of Variance (ANOVA). The experimental values of percentage removal were found to be in good agreement with the predicted values. pH value of 2, initial RY15 concentration of 50 mg L 21 and adsorbent dose of 50 mg are found to be the optimum conditions, for adsorption of RY15 from an aqueous solution. Thermodynamic parameters such as change in standard free energy change, enthalpy and entropy DG o , DH o , and DS o have been evaluated, and it has been found that the adsorption process is feasible, exothermic and spontaneous in nature. The experimental data were analyzed by the Langmuir, Freundlich, Sips and Temkin adsorption isotherms. Maximum monolayer adsorption capacity of the RY15 dye is found to be 138.6 mg g 21. The experimental data fitted well with the pseudo-second order kinetic model.

A novel chemically modified cellulose (DTD) adsorbent bearing pendent methyl benzalaniline chelating group was synthesized. This new adsorbent was used for the removal of Cu 2+ and Pb 2+ heavy metal ions from aqueous solution. The chemical and structural characteristics of the adsorbent were determined using FT-IR, 13 C CP-MAS NMR, SEM, EDX and TGA analysis. The adsorption parameters, such as pH, adsorbent dose, contact time, initial metal ion concentration and temperature were optimized. Adsorption kinetic parameters were fitted into pseudo-first-order and pseudo-second-order models. The kinetic data fitted well to the pseudo-second-order kinetic model. The adsorption isotherms such as Freundlich and Langmuir isotherms have been investigated. Thermodynamic parameters have also been evaluated. The negative values of ∆ 0 G and ∆ 0 H reveal that the adsorption system is spontaneous and exothermic in nature. The modified cellulose was challenged with microorganisms as a function of contact time. The biocidal results showed that the chemically modified cellulose has bactericidal effect against the bacterial species.

Novel azomethine-based polyester is synthesized and the structure of the products is confirmed by 1 H NMR, FT-IR, and XRD. The as synthesized polymer is employed as inhibitor against the corrosion of rebar in artificially simulated concrete pore solution with chloride contamination (blank) by means of Tafel polarization and electrochemical impedance measurements. First time in literature, azomethine polyester is employed as inhibitor for rebar corrosion. Polarization studies exhibited the maximum inhibition efficiency of 98% at 1000 ppm concentration. Electrochemical studies revealed the mixed-type nature of the inhibitors. The adsorption behavior of as synthesized polymeric inhibitor obeys Langmuir adsorption model. Mechanisms reveal the entire molecule is expected to adsorb on to the metal surface with near flat orientation and tend to arrange themselves parallel to each other covering the entire metal surface, hence, preventing the ingress of aggressive species to the metal surface. Further, SEM and atomic force microscope have proven the presence of adsorptive layer on the rebar under the simulated atmosphere.

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A series of new soluble, thermally stable polymers that contain phenylthiourea and azo groups in the polymer backbone were synthesized from a novel bisphenol and diacid chlorides. The novel bisphenol containing phenylthiourea and azo groups was synthesizedinthreesteps. In the first step, 4,4‘-bis(thiourea) biphenyl (BTB) was from 4,4‘-diaminobiphenyl and ammonium thiocynate. The second step involved the diazodization reaction of 4-aminophenol to give the diazonium chloride salt. The third step in the preparation of the monomer was the coupling of bisthiourea (BTB) with the diazonium chloride in the presence of an alkali which resulted in 4,4‘-bis( p-hydroxyphenyl azo thiourea)biphenyl (HP-ATB). The final step was the synthesis of polyesters by polycondensation reaction of this monomer with various acid chlorides (both aromatic and aliphatic). The materials were characterized by solution viscosity, UV-Vis, Fourier transform infrared spectroscopy, 1H NMR, differential scanning calorimetry and thermogravimetric analysis. Solubility of the polymers was also tested with different solvents, which can be an important parameter for the processability of the polymer. The synthesis and characterization of the novel monomer and polymers is discussed herein.