Adsorption of azo dyes using peanut hull and orange peel: a comparative study

Abstract

This work proposes the use of agro-industrial wastes, specifically peanut hull (HP) and orange peel (OP), as adsorbents for dyes, such as Remazol Golden Yellow RNL-150% (RYG), Gray Reactive BF-2R (RG) and Reactive Turquoise Q-G125 (RT). Characterization by Brunauer-Emmett-Teller indicates that the adsorbents are mesoporous, with pHzpc values of 5.0 for HP and 4.0 for OP. Fourier transform-infrared spectroscopy identified carbonyl and sulphonic groups. The initial pH of the best-adsorbing solution of the three colours was 2.0. Increasing the concentration of the adsorbent promoted an increase in the percentage of removal until saturation of the adsorbent. In a factorial design, the largest value of q was obtained with 0.25 g of the adsorbent, with a particle size of < 0.4 mm and a stirring speed of 300 rpm. Such conditions were used in kinetic studies and studies of adsorption equilibrium. The evolution kinetics were rapid in the first few minutes, and after 180 min the system reached equilibrium. The kinetic model that best fit the experimental data to a 95% confidence level for the F test was the pseudo-second-order model for RYG/HP, RG/OP and RT/OP. There was no significant difference between the kinetic models as evaluated by the F test for RYG/OP, RG/HP and RT/HP. The experimental results indicated favourable dye adsorption characteristics for the adsorbents studied. The results of the F test showed that for RYG and RG, there was no significant difference between the two evaluated models. This study suggests that HP and OP are viable alternatives for the treatment of effluents containing RYG, RG and RT dyes.

Agricultural peels for dye adsorption: A review of recent literature

“…The removal of RGY, RG and RT with adsorption onto orange peels was also investigated in a study of Nascimento et al [50]. The calculated BET surface area and the point of zero charge (pH ZPC ) were found to be 15.8 m 2 /g and 3.9, respectively.…”

Adsorption of anionic dyes from an aqueous solution by banana peel and green coconut mesocarp

“…The dye solutions (remazol golden yellow RNL-150% (RGY), reactive gray BF-2R (RG) and reactive turquoise Q-G125 (RT)) were prepared. The colour index (CI) names, CAS Registry Number, molecular formula and molecular weight of these dyes were reported by Nascimento et al [28].…”

Caracterização De Carvão Ativado Da Palha De Coqueiro E Avaliação Do Uso Na Remoção De Ácidos Naftênicos Presentes Em Mistura Modelo De Querosene De Aviação

“…Segundo Nascimento et al (2014), abaixo do pH pcz , o material apresenta cargas positivas na superfície favorecendo a adsorção de ânions, e consequentemente, acima do pH pcz , o material apresenta cargas negativas na superfície promovendo a adsorção de cátions.…”