Kinetics, Thermodynamics, and Equilibrium Studies on Adsorption of Reactive Red 198 from Textile Wastewater by Coral Limestone as a Natural Sorbent

Introduction: Dyes are among the most hazardous chemicals in industrial wastes due to their toxicity for aquaculture, reduction of light permeability, and in turn development of disorders in photosynthesis process. The current study aimed to investigate the efficiency of coral in removing red reactive 198 from textile dye wastewater was investigated. Materials & Methods: In this experimental study, the adsorption process was completed performed on a synthetic sample in a batch system Optimal conditions was also performed on the real wastewater of Yazdbaf textile factory. The effects of such parameters as the pH, dye's concentration, contact time, sorbent's dose, and temperature were investigated, following this, adsorption isotherms were determined and then the process was examined kinetically and thermodynamically. Next, the study data was analyzed by SPSS (ver, 21), EXCEL 2007, applying Pearson correlation coefficient. Results: The optimal conditions in removing the dye included pH=3, an equilibrium contact time of 120 min, 25 mg/L of the dye's concentration, and 3g/100mg of the sorbent's initial value. Under the optimal conditions, the dye's removal efficiency and the maximum adsorption capacity in the synthetic and real wastewater sample of Yazdbaf Company were 97.63%, 8.14 mg/g and 67.78%, 5mg/g respectively. The equilibrium data followed the Langmuir adsorption isotherm with a correlation coefficient of R2=0.96 and the adsorption's kinetics followed pseudo-second-order model with a correlation coefficient of 1 (R2=1). The thermodynamic investigations also indicated that the adsorption is of physical process and endothermic. Conclusion: As the results revealed, the good performance of the coral sorbent in removing dyes in aquatic environments, enjoying suitable density, having quick precipitation properties, not needing activation, and environmental safety of the process can encourage the efficiency of this adsorbent in treatment of dye-containing wastewaters

An overview of geological originated materials as a trend for adsorption in wastewater treatment

Adsorption is a unit operation widely used for the tertiary treatment of the most diverse effluents, whose mechanism is based on removing recalcitrant compounds from the organic and inorganic origin. In this process, choosing a suitable adsorbent is a fundamental point. This review article focuses on the adsorbents with natural geological origin: minerals, clays, geopolymers, and even wastes resulted from mining activity. Therefore, over 450 articles and research papers were explored. These materials' main sources are described, and their characteristics, composition, and intrinsic properties are related to adsorption. Herein, we discuss the effects of several process parameters, such as pH, temperature, pollutant, and adsorbent concentration. Furthermore, equilibrium, kinetics, and thermodynamic aspects are also addressed, and relevant regeneration prospects and final disposal. Finally, some suggestions and perspectives on applying these adsorbents in wastewater treatment are presented as future trends

Adsorbents for Water and Wastewater Treatment and Resource Recovery

Adsorption is a well-established operation used for water decontamination and the remediation of industrial effluents. It is also recognized as a key technology for recovering substances of economic interest or those at risk of scarcity. The new sustainability paradigm of the circular economy and the current context of promoting the efficient use of natural resources, water and energy have been motivating the search for eco-friendly adsorbents for water and wastewater treatment and resource recovery. This Special Issue compiles 21 papers (17 research articles and 4 reviews), addressing the removal of heavy metals, toxic metalloids, precious metals and organics from aqueous solution, using a wide variety of adsorbents derived from natural and waste materials