Efficient removal of crystal violet dye from aqueous solutions by vitreous tuff mineral.

Textural, structural and morphological characteristics of the vitreous tuff were determined by means of several physicochemical techniques. The nitrogen adsorption isotherm at 77 K was fitted with the Brunnauer-Emmet-Teller model and together with the results of the average pore distribution showed a mesoporous material. Samples of vitreous tuff were used as adsorbent to study the removal of crystal violet from aqueous solution. The presence of -OH moieties in the material seems to be responsible for the removal of the dye showing that vitreous tuff can be used as an organic dye adsorbent material. The pseudo-second-order model was the best fit model for describing the sorption process of crystal violet; intraparticle diffusion being the controlling step in the process. The experimental adsorption isotherm was fitted with Langmuir, Freundlich and Langmuir-Freundlich models, showing better correlation with the second one. The adsorption capacity was 170.01 mg/g, being among the highest compared with other inorganic and organic common sorbent materials. The design of single stage of the adsorber can predict the behaviour to potential scale up. This mineral has a very good potential as an adsorbent material for organic dyes.

As(III) and As(V) sorption on iron-modified non-pyrolyzed and pyrolyzed biomass from Petroselinum crispum (parsley).

The sorption of As(III) and As(V) from aqueous solutions onto iron-modified Petroselinum crispum (PCFe) and iron-modified carbonaceous material from the pyrolysis of P. crispum (PCTTFe) was investigated. The modified sorbents were characterized with scanning electron microscopy. The sorbent elemental composition was determined with energy-dispersive X-ray spectroscopy (EDS). The principal functional groups from the sorbents were determined with FT-IR. The specific surfaces and points of zero charge (pzc) of the materials were also determined. As(III) and As(V) sorption onto the modified sorbents were performed in a batch system. After the sorption process, the As content in the liquid and solid phases was determined with atomic absorption and neutron activation analyses, respectively. After the arsenic sorption processes, the desorption of Fe from PCFe and PCTTFe was verified with atomic absorption spectrometry. The morphology of PC changed after iron modification. The specific area and pzc differed significantly between the iron-modified non-pyrolyzed and pyrolyzed P. crispum. The kinetics of the arsenite and arsenate sorption processes were described with a pseudo-second-order model. The Langmuir-Freundlich model provided the isotherms with the best fit. Less than 0.02% of the Fe was desorbed from the PCFe and PCTTFe after the As(III) and As(V) sorption processes.

Adsorption of cadmium by Na and Fe modified zeolitic tuffs and carbonaceous material from pyrolyzed sewage sludge.

In the present study the process of adsorption of cadmium from aqueous solutions using Na-zeolitic tuff, Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge treated with HCl was investigated. The cadmium removal efficiency was studied as a function of contact time, adsorbate concentration, pH and adsorbent dose. The results showed that removal of cadmium was best described by the Langmuir-Freundlich isotherm. The kinetic experimental results were best described by the pseudo-first order model. The results indicate that the adsorption mechanism is physical and chemical sorption on heterogeneous materials. The maximum retention of cadmium was at pH around 6.0 for the materials. In kinetic studies, the Na and Fe modified zeolitic tuffs showed similar sorption capacities for cadmium and they were higher than the capacity found for carbonaceous material.

Effect of the pH and temperature on the biosorption of lead(II) and cadmium(II) by sodium-modified stalk sponge of Zea mays.

OBJECTIVE: The present work was carried out to investigate the effects of temperature, initial pH, initial concentration, and contact time on the biosorption of lead (Pb) and cadmium (Cd) by modified stalk sponge of Zea mays using a batch technique. METHODS: The biomass was chemically modified with a 0.1 M NaCl solution. The lead and cadmium sorption process was evaluated at 20°C, 30°C, 40°C, and 50°C. RESULTS: The results showed that the modified stalk sponge of Z. mays had a good capacity for biosorption of Pb(II) and Cd(II). The kinetic behavior was described by the pseudo-second-order model for both metallic species. The experimental isotherms obtained at different temperatures were fit with Langmuir and Freundlich models. Thermodynamic parameters ΔH(0) and ΔS(0) were calculated using the van't Hoff equation, and the results show that Pb(II) and Cd(II) sorption by modified stalk sponge of Z. mays is an exothermic and spontaneous process.

Biosorption of lead by maize (Zea mays) stalk sponge.

This study investigated the removal of Pb(II) from aqueous solutions by a maize (Zea mays) stalk sponge. Equilibrium and kinetic models for Pb(II) sorption were developed by considering the effect of the contact time and concentration at the optimum pH of 6 +/- 0.2. The Freundlich model was found to describe the sorption energetics of Pb(II) by Z. mays stalk sponge, and a maximum Pb(II) loading capacity of 80 mg g(-1) was determined. The kinetic parameters were obtained by fitting data from experiments measuring the effect of contact time on adsorption capacity into pseudo-first and second-order equations. The kinetics of Pb(II) sorption onto Z. mays biosorbent were well defined using linearity coefficients (R(2)) by the pseudo-second-order equation (0.9998). The results obtained showed that Zea may stalk sponge was a useful biomaterial for Pb(II) sorption and that pH has an important effect on metal biosorption capacity.

Comparison of Cd-Pb adsorption on commercial activated carbon and carbonaceous material from pyrolysed sewage sludge in column system.

The sorption behaviour of Cd and Pb from aqueous solutions in columns, using both commercial activated carbon and a carbonaceous material from pyrolysis of sewage sludge, was determined. The breakthrough data obtained for Cd and Pb sorption could be described by the linear form of the Thomas adsorption model. The breakthrough capacities found from column studies were different for each metal and the data reflect the order of metal affinity for the adsorbents materials. The adsorption capacity of the carbonaceous material was higher for cadmium than for lead in a single system and in binary systems, and, for activated carbon, the sorption capacities of lead and cadmium were similar in the binary system. The results indicated that the carbonaceous material from pyrolysis of sewage sludge is a better adsorbent than activated carbon of cadmium and lead.

Sorption of indigo carmine by a Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge.

Indigo carmine removal from aqueous solution has been evaluated using Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge treated with HCl (CM). The adsorbents were characterized by scanning electron microscopy, BET surface area and X-ray diffraction. Sorption kinetics and isotherms were determined and the adsorption behaviors analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results obtained with the Fe-zeolitic material, while kinetic first order and Langmuir-Freundlich models were applied to the results from the carbonaceous materials. This indicates mechanisms of chemisorption and physical sorption, respectively, on the heterogeneous materials. The results indicate that the carbonaceous material from the pyrolysis of sewage sludge (sorption capacity 92.83 mg/g) is a better adsorbent of indigo carmine than the zeolitic material (sorption capacity 32.83 mg/g).

Cr(VI) removal from wastewater using low cost sorbent materials: roots of Typha latifolia and ashes.

This work presents conditions for hexavalent chromium (Cr(VI)) removal from aqueous solution using different sorbent materials, namely: pyrolytic ashes of an industrial sludge from wastewater treatment and roots of Typha latifolia. The sorbent materials were characterized using scanning electron microscopy (SEM) and surface area using the Brunauer-Emmett-Teller (BET) technique, before and after the contact with the chromium-containing aqueous media. An overall Cr(VI) concentration reduction of 45% was achieved using the roots of Typha latifolia whereas in the case of pyrolytic ashes a 60% removal was observed. The percentage removal was found to depend on the initial Cr(VI) concentration in aqueous solution, pH and temperature. The Cr(VI) uptake process was maximum at pH 2 and a temperature of 40 degrees C for both sorbents. These materials showed a Cr(VI) adsorption capacity that was adequately described by the Langmuir adsorption isotherm. It was demonstrated that the use of waste materials for the treatment of Cr(VI)-containing wastewater is an effective and economical alternative method.