ADSORÇÃO DE AZUL DE METILENO DE SOLUÇÃO AQUOSA EM BIOCARVÃO ATIVADO DERIVADO DE PALHA DE ARROZ E CASCA DE COCO

Abstract

Removing dyes from wastewater is essential for environmental protection. The presence of dyes in water bodies can cause serious damage to the aquatic ecosystem and compromise the potability of the water. Therefore, it is necessary to develop efficient and low-cost techniques for treating wastewater containing such compounds. Adsorption with biochars has gained prominence due to its simplicity, low cost and high applicability. This study aimed to evaluate the removal of methylene blue (MB) dye using rice straw activated biochar (BCR) and coconut husk (BCC). The biochars were produced through the pyrolysis of biomass in an atmosphere of nitrogen gas (N2) at 500 ºC and were activated with 1M NaOH. The adsorption capacity followed the following sequence: commercial activated carbon (CA) > activated BCA > BCA > BCC > activated BCC at a temperature of 30º C. The maximum adsorption capacity of CA, activated BCA, BCA, BCC and activated BCC was 100.09 mg g-1, 59.97 mg g-1, 4.38 mg g-1, 2.75 mg g-1 and 1.1 mg g-1, respectively. The adsorption of MB dye was favored with increasing pH and temperature of the solution. The pseudo-second-order adsorption (PSO) kinetic model described the MB adsorption process well, indicating that adsorption occurs through the chemisorption mechanism. The Langmuir isotherm best suited the experimental data, indicating that adsorption occurs in monolayers and with a uniform distribution of active sites. Thermodynamic analysis indicated that the AM adsorption process with activated CA and BCA is spontaneous and endothermic.