In this work, spent coffee grounds (SCG) were treated using sulfuric acid hydrolysis in order to isolate the sulfuric acid lignin (SAL). The reactivity of SAL was improved through phenolation and acetylation. Spectroscopic analysis showed that the isolated lignin is composed of GHS type and it was characterized by a high amount of (C–C) and β-O-4 bonds. The thermal analysis showed that the phenolated sulfuric acid lignin (Ph-SAL) present higher thermal stability compared to SAL and acetylated sulfuric acid lignin. In addition, the phenolic hydroxyl group content increases from 2.99 to 9.49 mmol/g after phenolation. Moreover, a methylene blue (MB) adsorption test was established in order to find out the sorption capacity of different samples. The study showed that the adsorbed amount of dye increase after the chemical modification of SAL, especially after phenolation. The removal efficiency was enhanced after modification to reach 99.62% for Ph-SAL. The evaluation of the adsorption experimental data with the theoretical models of Langmuir and Freundlich showed that the best fitting was expressed by the Langmuir model for all samples. Finally, this study showed that lignin isolated from SCG can be simply and easily chemical modified and exhibits excellent adsorption ability towards cationic dyes (MB) in aqueous solutions. As a renewable, low-cost, and natural biomass material, lignin from SCG shows a promising practical and economical application of biomass in the field of wastewater purification.
The gliding arc discharge plasma (GAD) technique was used for discoloration and degradation of an anthraquinone dye Alizarin red S (ARS), an azo dye Orange G (OG) and their mixture. The influence of chloride and sulfate salts on the efficiency of treatment has also been studied. The aim of this study is the discoloration and degradation by GAD of ARS, and OG and their mixture.The GAD plasma generated between two moist air metallic electrodes connected to a high voltage produced chemical species and highly reactive molecules Å OH, NO Å , O Å , O 2 , HO 2 Å , H Å , H 2 O 2 , O 3 . . . and other excited-state neutral molecules. The reactions of discoloration for ARS and OG followed pseudo-first-order kinetics. The apparent kinetic constants of bleaching were found equal to 0.014 and 0.013 min À1 and degradation of 0.008 and 0.010 min À1 , respectively for the ARS and OG. For mixtures, the rate of discoloration was 80% in 120 min of treatment for mixtures III, IV and V, while the rate of COD reduction was fast in the first 30 min since it varied between 35% and 40% for all mixtures but stabilized at 68% toward the end of the treatment. The addition of chloride salts and sulfate showed a decrease in the effectiveness of treatment.
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