Remoção de azul de metileno por adsorção usando pó de serragem do gênero Pinus sp.

Abstract

This work sought to evaluate the use of sawdust powder (SP) Pinus sp. genus as adsorbent material on the removal of methylene blue (MB) in the concentration of 0.15 g/L, as an alternative for granular activated carbon (GAC). Batch assays were carried out varying adsorbent SP and GAC masses (0.10 g, 0.25 g, 0.5 g, 0.75 g and 1.0 g), temperature (30 °C, 40 °C and 50 °C) and effluent pH (5.5; 6.5; 7.5 and 8.5). The same assays were conducted with the sawdust powder treated with 1% formaldehyde (SPF) and 1% sulphuric acid (SPSA). Fitting of the experimental data was done with pseudo-first order model of Lagergren and pseudo-second order. The isotherm was obtained from Giles classification. Physical-chemical characterization of SP and GAC were carried out of: pH (ASTM D 3838-80/1999), apparent density (NBR 12076/1991), iodine number (NBR 12073/1991), moisture content (ASTM D 2867-04), ash content (ASTM D 2866-94/1999), volatile material (ASTM D 5832-98/2003), superficial area by BET method (Brunauer, Emmett, Teller), volume and size pores by BJH method (Barrett, Joyner-Halenda). Batch assays were conducted according to Lin (1993) to SP, Kannan e Sundaram (2001) to GAC, Garg et al. (2004) to SPS and Tumlos et al. (2011) to SPSA. Results indicated: acid character to SP (pH 4.1±0.06) and GAC (pH 6.24±0.10); iodine number higher than the minimum value recommended of 600 mg/g by ABNT to SP (660±0.85 mg/g) and GAC (650±3.06 mg/g); superficial area classified as micropore to SP and mesopore to GAC. Results of the batch assays indicated: optimum mass of 1.00 g with 81.6% (30 °C), 81.8% (40 °C) and 79.9 % (50 °C) to SP of MB removal; optimum pH of 7.5. Results of assays with SPF, SPSA and GAC indicated that SPF presented efficiencies of 81.92% (40 °C) and 89.75 % (50°C) and with GAC with 58.34 % (30 °C), 64.59 % (40 °C) and 64.44 % (50 °C) in the removal of MB dye. Pseudo-second order kinetics model better described adsorption at 50 °C (R2 = 0.999). Isotherms were classified as Langmuir (subgroup 1) to SP and Sigmoid (subgroup 3) to GAC, with adsorption in homogeneous monolayer and with affinity of MB to SP; and filling of the second layer and with the solute adsorbed into sets to GAC. It was possible to conclude that Pinus sp., genus, sawdust powder is efficient in the removal of color from aqueous solution containing methylene blue by adsorption process.