Potential Low-Cost Biosorbent Modified from Yard Waste for Acid-Fuchsin Removal

Abstract

Recently, eco-efficiency and cost-effectiveness biosorbents have been a hot topic in the research fields of environmental engineering and material science. In this work, the modification of the two common yard wastes (elm branches and turfgrass) included a process where the waste was oven-dried at 90°C for 12 h, milled and sieved through 0.25 mm, and soaked in 1 mol·L−1 sodium citrate with a mass ratio of 1∶3 for 24 h to hydrolyze protein. The adsorption potential of prepared biosorbents toward acid fuchsin (AF) were tested and compared with commercial activated carbon (AC). The effects of doses, pH, and initial concentration of AF were investigated and the appropriated parameters for adsorption were obtained. The adsorption thermodynamics and kinetics showed that the rates of adsorption by modified branches (MB) and modified turfgrass (MG) are rapid and efficient, superior to AC. The best adsorption parameters found in the experimental tests are as follows: pH 4, temperature 35°C, initial concentration of AF solution of 40 mg·L−1, and modified biosorbents of 400 mg·L−1. In practical application, pH 5 and a temperature of 25°C could hold promise to adsorb the dye. The MG and MB showed more pore and mesoporous structures than raw materials according to scanning electron microscope (SEM). In the processes of adsorption, AF mainly reacted with benzene ring skeleton, C─ C, heterocyclic compounds, ─ OH, ─ CH, C─ O, P─ C─ O, and Si═O. Fourier transform infrared spectrometry (FTIR) analysis indicates the peak area changes of MG and MB are consisting with the Qm calculated by Langmuir model due to the higher binding capacities of carboxyl and phenolic groups. The maximum sorption capacities (Qm) of the both prepared biosorbents are above 142.76 mg·g−1, presenting comparative adsorption capacities to the reported various patterns of biosorpents. This work prepared potential low-cost biosorbents with comparative sorption capacities by easy physical and chemical modification and provide an eco-efficiency and cost-effectiveness way to promote the sustainable management and the reuse of these city raw lignocellulosic waste.