Gilvanise Alves Tito

Cadmium and copper adsorption on bentonite: effects of pH and particle size

Reactions of heavy metals with clay minerals are important in determining metal fates in the environment. However, the adsorption process of these metals by the bentonite has been extensively investigated. The objectives of this work were to assess the ability of bentonite clay to adsorb cadmium and copper and to study the effects of pH and particle size upon these metals adsorption. Adsorption isotherms were obtained from batch adsorption experiments, with increasing cadmium and copper concentrations (5-200 mg L-1). To find out the effects of pH and particle size on adsorption, the experiments were conducted at pH 4; 5 and 6 using particles sizes of < 0.5 mm and 0.5 to 2.0 mm . The difference between initial and final cadmium and copper concentrations was assumed to be the amount adsorbed by bentonite. The bentonite adsorbed more copper than cadmium, both metals adsorption increased with increasing pH for both particle sizes. No effect of particle size was observed. Experimental data were best fitted to Langmuir model.

Mobilidade do zinco e do cobre em Argissolo com aplicação de argila bentonita

The mobility of heavy metals in the soil is influenced by the soil, the clay mineralogy and the amount of metal. Aiming to evaluate the effect of bentonite clay on zinc and copper mobility, leaching columns of soil, filled with an Argisol, utilising increasing doses of bentonite (0, 30 e 60 t ha-1) and concentrations of zinc and copper (50, 250 e 450 mg kg-1) were submitted to a saturated and steady flow. The flux density, velocity, transport retardation factor, dispersion-diffusion coefficient and breakthrough curves were obtained. The transport parameters were determined using the DISP computational model. The results allow to conclude that the application of bentonite clay to the soil promoted the retention of the zinc and copper, mainly the last one, decreasing the concentration in leachate and reducing potential contamination risks. The bentonite clay application increased the soil retardation factor and decreased the dispersion-diffusion coefficients of the soil.

Phytomass of beans and grain production as affected by zinc, copper and cadmium doses and bentonite application

The objective of this study was to determine the effect of zinc, copper and cadmium on phytomass and grain production and to evaluate indirectly the adsorbent effect of bentonite clay by determining the accumulation of these heavy metals in bean plants. The study consisted of three separate experiments (one for each cation) with the application of three doses of bentonite (0, 30 and 60 t ha-1) in pots containing separately 50 mg of Zn; Cu and Cd kg-1 of soil, with three replicates. Thus, each experiment consisted of 9 experimental units. In each one, a bean plant was cultivated and after 65 days, samples of leaves, stems, roots and grains were collected. Afterwards, the samples were dried, weighed, grinded and the concentrations of Zn, Cu and Cd were determined. The phytomass of leaves of the plant growing on the soil with Zn, the Zn concentration in the whole plant and the Cd concentration in the leaves, stem and grains were significantly influenced by the bentonite application. Zn and Cd concentration in leaves, stem and grains decreased with the application of bentonite, indicating a positive effect of the clay application to the soil on the adsorption of these metals, decreasing the availability for plants. Zn was the most accumulated element in the plant, followed by Cd and Cu. The Zn, Cu and Cd accumulation in the plant obeyed the following sequence: stem > leaves > grains > roots; roots > stem > grains > leaves; roots > stem > leaves > grains, respectively.

Uso de bentonita na remediação de solos contaminados com zinco: efeito na produção de feijão

Several procedures have been proposed to reduce the concentration of heavy metals in soils and consequently, to reduce polluting effects. One of the most used procedures is the application of materials such as bentonite capable of adsorbing these elements making them less available to plants. The objective of this study was to evaluate the ability of bentonite in the remediation of soils contaminated with zinc. An experiment was carried out in a greenhouse in a completely randomized design with three replications, using cowpea (Vigna unguiculata L.) as an indicator plant. Treatments consisted of a 3 x 3 factorial, the first factor being three doses of Zn (50, 250 and 450 mg kg-1) and the second factor three doses of bentonite (0, 30 and 60 t ha-1). For the study pots with 18 kg filled with 15 kg of soil mixed with the respective doses of bentonite and zinc were used. After ten days of soil incubation the bean seeds were sown. After sixty five days leaves, stems, roots, seeds and bark were harvested separately, dried in air circulation oven at 65 °C, weighed, grinded and analyzed for zinc. The results showed that the bentonite seems to be an optimum inorganic material for remediation of soils contaminated with zinc. The incorporation of bentonite to the soil increases the adsorption of zinc by decreasing the availability of this element for the plant tending therefore to increase the production of dry matter.

Soil Chemical Amendments and the Macronutrients Mobility Evaluation in Oxisol Treated With Biochar

Biochar is material produced during a process called pyrolysis. This material can be used as fertilizer to increase the agronomic productivity of low fertility soils. The objective of this study was to evaluate the soil chemical amendments and the macronutrients leaching following biochar application, produced from poultry litter, in Yellow Red Latosol in laboratory experiments. Soil columns (height 20 cm) containing 0; 10; 15; 20; 25 and 30 t ha-1 of biochar with four replications totaled 24 experimental units. For 30 days, water was applied daily to each column, and the leachates were collected and chemically characterized. After this period, soil samples were taken from the 0-10 and 10-20 cm layer depth and chemically characterized. Biochar reduced exchangeable acidity values. Biochar improved soil fertility. Leachates contained increasing EC, K, Na, Ca and Mg, however the concentration of these elements were small in relation to the biochar doses.

Crambe Growth in a Soil Amended with Biochar and under Saline Irrigation

ABSTRACT Biochar is the term given to biomass subjected to the process of change in the composition by the action of high temperatures. Advantages of biochar in soil quality have been reported, including amelioration of salinity effects. Crambe has great potential to figure as raw material for biofuel, since it naturally contains up to 60% of erucic acid. This study evaluated crambe growth in a soil amended with biochar and irrigated with saline waters. A greenhouse experiment was conducted following a completely randomized design with five levels of biochar, two irrigation water supplies, and four replications. Parameters related to soil chemical properties, crambe growth, oil, and macronutrient contents were evaluated. Biochar presented significance for pH, electrical conductivity (EC), organic matter (OM), phosphorus (P), sodium (Na), and potassium (K) contents. Crambe growth parameters decreased with the doses of biochar. Oil and macronutrient contents were in accordance to previous studies.