In the present study, a high-surface area activated carbon was prepared by chemical activation of lemon peel with H3PO4 as the active agent. Then, the adsorption behavior of Malachite green dye and Pb(II) ions on the produced activated carbon was studied. Batch process was employed for sorption kinetics and equilibrium studies. Experimental data were �tted to various isotherm models. According to the Langmuir model, the maximum adsorption capacities of Malachite green dye and Pb(II) ions were found to be 66.67 and 90.91 mg g-1, respectively, at room temperature. Kinetic studies showed the adsorption process followed a pseudo second-order rate model. The sorption kinetics were controlled by intra-particle diffusion. The results indicated that the produced activated carbon can be economically and effectively used as an adsorbent for the removal of Malachite green dye and Pb(II) ions from wastewaters.

In the present article, a simple, rapid, selective, sensitive and economical method has been developed for the separation/preconcentration of the trace amounts of Pd(II) in different real samples using alumina coated magnetite nanoparticles modified by sodium dodecyl sulfate and its determination by flame atomic absorption spectrometry after eluting with 1.0 mol L-1 thiourea. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation of Pd(II) were 280 (for 700 mL of sample solution), 4.3 ng mL-1, 6.0 - 120.0 ng mL-1 and 4.6% (for 10 ng mL-1, n=10), respectively.

Um novo método de extração em fase sólida foi desenvolvido para separar e pré-concentrar traços de tensoativos catiônicos, tais como, brometo de dodeciltrimetilamônio (DTAB), brometo de cetiltrimetilamônio (CTAB) e cloreto de cetilpiridínio (CPC). Esse método é baseado na sorção do tensoativo aniônico (AS-), dodecilssulfato de sódio (SDS), sobre a superfície de γ-alumina, enquanto um cartucho C18 é utilizado para a pré-concentração dos tensoativos catiônicos (CS+). O método espectrofotométrico, utilizado para a determinação dos tensoativos catiônicos, baseia-se na competição entre o corante catiônico, azul de metileno (MB+), e o CS+, para associação e formação do complexo SDS. O íon complexo formado (MB+) pode ser quantitativamente substituído pelo CS+, levando a um aumento da absorvância medida em 662 nm. Foram estabelecidas ótimas condições experimentais para a separação, pré-concentração e determinação dos tensoativos catiônicos. Sob essas condições otimizadas, realizou-se a pré-concentração (2×) e os resultados mostraram que a determinação do CPC, DTAB e CTAB poderia ser realizada nas faixas de concentração de 1×10-5-2×10-4, 4×10-5-5×10-4 and 5×10-5-5×10-4 mol L-1, respectivamente. Por fim, a partir de onze determinações de 10,0 mg mL-1 das soluções de CPC, DTAB e CTAB obtiveram-se RSDs de 4,3, 3,7 e 4,0%, respectivamente. O método foi validado por meio de um conjunto de diferentes amostras que continham os tensoativos catiônicos.

A new solid phase extraction method has been developed to the separation and preconcentration of trace amounts of cationic surfactants i.e. dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC). This method is based on the sorption of anionic surfactant (AS-) of sodium dodecyl sulfate (SDS) on the γ-alumina surface and C18 cartridge is used for preconcentration of cationic surfactants (CS+). Spectrophotometric determination method used for the determination of cationic surfactants is based on the competition between the cationic dye of methylene blue (MB+) and CS+ for association complex formation with SDS. The MB+in the ion associate complex can be quantitatively substituted by CS+ leading to an increase in the absorbance measured at 662 nm. Optimum experimental conditions for separation, preconcentration and determination of cationic surfactants have been reported. Under the selected optimal conditions, preconcentration factor of two-fold was achieved and the results showed that determination of CPC, DTAB and CTAB could be performed in concentration ranges of 1×10-5-2×10-4, 4×10-5-5×10-4 and 5×10-5-5×10-4 mol L-1, respectively. Eleven determinations of 10.0 mg mL-1 of CPC, DTAB and CTAB solutions led to RSD's of 4.3, 3.7 and 4.0%, respectively. Method was validated using a set of different samples containing cationic surfactants.