Abstract
Rape straw, an agricultural by-product, was modified with citric acid (CA) to adsorb the cationic dye crystal violet (CV) from an aqueous solution. The morphology and surface properties of the adsorbent were observed by scanning electron microscopy (SEM) and X-ray photoelectron analysis (XPS). The experimental conditions were optimized by the effects of initial pH, adsorbent dosage, dye concentration and contact time. The results showed that CA-modified rape straw had a higher adsorption capacity for crystal violet (CV) compared to pristine rapes straw; at pH 3.0 Âą 0.15 the removal ratio increased up to 98.30% Âą 5.80%. This study provides a detailed comparison of the contact time curve with different dye concentrations. The results showed that the CV removal rate of modified rape straw was increased by 97.43% Âą 0.25%, 99.09% Âą 0.61% and 99.11% Âą 2.20% respectively within 30 min at high and low concentrations. Langmuir isotherm proved to be the most appropriate analytical method to predict the experimental results. The maximum adsorption capacity was 1012.62 Âą 6.40 mg gâ1. The kinetic process of crystal violet adsorption on the new adsorbent was investigated using a model based on pseudo-first and pseudo-second order. The good fit correlation coefficient R2 ⼠0.99 suggested that the pseudo-second order model has a good affinity with the adsorption mechanism.
Published Version
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