SILVA, J. V. N.; http://lattes.cnpq.br/4735394040147922; SILVA, José Vanderley do Nascimento.
Résumé:
The increase in industrial production has provided the generation of wastewater
contaminated with heavy metal ions. These must be treated before disposal into the
environment. For this reason it is very important to the use of processes to reduce or
eliminate heavy metals from industrial effluents. Among the many existing processes,
adsorption has great efficiency in the removal of metals present in low
concentrations. Clays have shown excellent results in heavy metal adsorption
processes, which motivates the search for clays having higher affinity with each type
of metal. In this work the smectite clays natural Chocobofe and Chocolate B from the
state of Paraíba were investigated in order to evaluate their affinity and capacity for
the removal of cadmium, lead and zinc. Held, initially, the characterization of clays by
techniques: X-ray diffraction; Chemical analysis; Thermal analysis (differential and
gravimetric); Spectroscopy in the infrared region; Adsorption Nitrogen Physics;
Scanning electron microscopy and capacity of cation exchange. After characterized
the clays were evaluated for removal capacity (q and q) and its removal percentage
(% Rem) to metals (cadmium, lead and zinc) present in synthetic wastewater through
finite bath system. In order to achieve greater efficiency in the removal of metals a 22
factorial experimental design was conducted to evaluate two input variables: initial
concentration of heavy metals (10, 30 and 50 ppm) and pH (3, 4 and 5) to determine
the best working conditions, which revealed that the pH = 5 and initial concentration
of 50 mg/g were the conditions that showed better results from 88.54 to 99.44%
reaching values of percentage removal and 3,36- 4.43 mg/g of removability. From
these data were developed kinetic and equilibrium isotherms that served data to
evaluate the adsorption capacity of clays with adjustments made through the
Langmuir, Freundlich and Redlich-Peterson. The results of the kinetic tests indicated
that the removal of Cd2+ ions, Pb2+ and Zn2+ the clay are applied to the mechanism of
the pseudo-second-order rate model, a time of 10 minutes is required to reach
equilibrium. The mathematical models used to model the experimental data
adequately describe the dynamics of adsorption, producing theoretical isotherms
quite close to those found behavior with experimental isotherms and that of the
models used, it appears that the Langmuir and Redlich-Peterson showed better fit to
the experimental data. The maximum adsorption capacity obtained by clays
Chocobofe and Chocolate B were 18.35 -21.88 mg. g-1 for Pb2+; 10.0 to 11.20 mg. g-1
for Cd2+; 8.64 to 8.69 mg.g-1 for Zn2+, indicating a selectivity of clays in relation to
studying a metal affinity sequence: Pb2+> Cd2+> Zn2+. Thus, the experimental results
indicate that the bentonite clays can be used as adsorbents for the removal of metals
cadmium, lead and zinc contaminated water and effluent by adsorption mechanism.
