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In recent years, water pollution has become a major problem, especially due to the wastes discharged from different sectors without treatment. Among these, there are various paint wastes used by the textile, leather, paper and cosmetics sectors. Crystal violet (CV) is a widely known cationic dye and is often used as a colorant in industries. CV dye is known to be toxic to humans and animals at 1 ppb. For this reason, it is very important for environmental safety to treat industrial wastewater from crystal violet before discharge. This research aimed to evaluate the efficacy of two different montmorillonite-based nanoclays (B1 and B2) as a low-cost material for the removal of crystal violet dye from aqueous solutions. Structural characterizations of nanoclays were analyzed using FTIR and TGA methods. All parameters that could affect the CV adsorption process were optimized in a batch system. The effects of various factors (adsorbent dose, contact time, solution pH, co-existing ion effects, adsorption temperature, initial dye concentration) on the adsorption process were investigated. Experiments to investigate the mechanism of the CV-nanoclay adsorption system showed that the adsorption kinetics and equilibrium parameters fit better with the Pseudo second-order kinetic model and the Langmuir isotherm model, respectively. The maximum adsorption capacities (qm) of B1 and B2 adsorbents were obtained as 224.63 mg/g at 25°C and 360.30 mg/g at 45°C, respectively. A suitable combination of surface and CV ion charge was obtained at low pH values (=7) of the CV solution. The presence of co-existing NaCl ions did not significantly affect the CV adsorption capacity. When the results were evaluated, it was seen that the montmorillonite-based adsorbents were effective and cost-effective adsorbents for CV dye removal. [ABSTRACT FROM AUTHOR]

The toxicity of antibiotic residues in water resources adversely affects the environment. Recent studies have focused on the removal of organic pollutants such as antibiotics from aqueous solutions with cheap and environmentally compatible adsorbents. In this study, adsorption of oxytetracycline hydrochloride (OTCHCL) on the natural Manisa-Gördes clinoptilolite was investigated in the batch system at 298-323 K. Effects of pH, initial concentration, adsorbent dosage, contact time, stirring speed and temperature on adsorption were examined and optimum parameters were determined. Isotherm models including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin were applied to analyze the adsorption data. Kinetic constants were determined by pseudo-first order (PFO), pseudo-second order (PSO), intraparticle diffusion and Elovich models. Adsorption of OTC-HCL on natural zeolite fitted well to the Freundlich and pseudo-second order models. The maximum adsorption capacity of natural zeolite was determined as 60.97 mg/g at 323 K. Thermodynamic studies indicated that the adsorption of OTC-HCL on natural zeolite was spontaneous and endothermic. Physicochemical characterization of natural zeolite was conducted by N2 adsorptiondesorption, XRD, FTIR, SEM-EDX analyses before and after adsorption. SBET, specific surface area of the natural zeolite decreased after adsorption process. Characterization results showed that OTC-HCL molecules were successfully adsorbed on the natural zeolite surface. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatite material was prepared for the removal of Remazol N.Blue RGB (RB203) from waters. In the synthesis of hydroxyapatite material, waste hen's eggshell was evaluated as calcium source. Synthesis of hydroxyapatites was performed at three different pH values (pH 9, 10 and 11) using precipitation method. Before and after calcination of eggshells, XRF, XRD and SEM analysis were carried out. Synthesized hydroxyapatites were characterized by TGA-DTA, XRD and FTIR analysis. At the end of the characterization studies, hydroxyapatite structure was obtained better in pH 10 medium, and adsorption studies were carried out with the material prepared at this pH value. The effects of pH (2-12), amount of sorbent (2-10 g/L) and concentration of dye (25-200 mg/L) on adsorption of RB203 using hydroxyapatite were examined. In order to determine the mechanism of adsorption, the Langmuir, Freundlich, Temkin and Henry isoterm equations were used. Comparing the adsorption isotherms in terms of correlation coefficients (R2), it was seen that the Langmuir, Freundlich and Temkin isotherm models were in good agreement with the experimental data. The highest adsorption capacity obtained with the Langmuir isotherm model was 27.93 mg/g. In order to examine the adsorption kinetics, the pseudo-first and the second order kinetic equations were used. The results of adsorption kinetics show that the adsorption of RB203 with hydroxyapatite was better expressed by the pseudo-second order kinetic equation. This study shows that the hydroxyapatite synthesized from waste calcined eggshell is a promising sorbent for adsorption of dye. [ABSTRACT FROM AUTHOR]

The removal of Ni(II) and Cr(VI) ions from aqueous solutions using chemically modified apricot kernel shells (P. armeniaca L.) was investigated in this research. Chemical modification methods effects on the adsorption capacity improvement for removal of heavy metals have been investigated. Structures of apricot kernel shells materials before and after modifications was examined by the FTIR and SEM analyses. HCl, NaOH and Fenton reactives were used for the modification processes. The investigation of kinetic, isotherm and thermodynamic parameters were also studied for HCl, NaOH and Fenton modified apricot kernel shells The rejeneration processes were studied for the determination of apricot kernel shells' reusability after the adsorption processes. Additional costs for applied modification processes were calculated and they were compared with the classical methods. The chemical oxygen demand (COD) residues in treated water by raw apricot kernel shells materials decreased from 910-1430 mg/L to 10-90 mg/L with the modification processes. The removal efficiencies changed with heavy metal concentration in water sample and increased up to 92% for apricot kernel shells materials. The adsorption capacities were found between 1 mg/g and 90 mg/g according to type of adsorbent and modification methods. As a result, it was revealed that adsorption capacities and costs of apricot kernel shells were compatible with conventional adsorbents. [ABSTRACT FROM AUTHOR]