Corncobs as a potentially low-cost biosorbent for sulfamethoxazole removal from aqueous solution

Maize cob (Zea mays) as natural biomass sorbent for crude oil biosorptive removal from contaminated seawater: Taguchi process optimization and biosorptive removal mechanism

Crude oil pollution poses a serious threat to the aquatic environment. Hence, there is an increasing interest in developing an efficient cleaner process technique for oil spill cleanup via agricultural biomass waste-organic sorbent utilization. This work evaluated the effects of independent biosorptive removal at three varying levels (initial concentration of crude oil (Z1, 7.8-15.6 g/L), seawater-oil temperature (Z2, 25-45 °C), sorbent dose (Z3, 1-3 g), and sorbent particle size diameter (Z4, 1.18-4.72 mm)) on the biosorptive removal efficiency and biosorptive capacity performance of maize cob sorbent for crude oil biosorptive removal from seawater. Experiments were designed based on Taguchi orthogonal array experimental design (L9(34)) to study the effects and process optimization. The results revealed that the maize cob sorbent's crude oil biosorptive removal efficiency is related to Z1, Z3, and Z4, while the biosorptive capacity is related to Z1 and Z3. The optimum biosorptive removal efficiency and the biosorptive capacity values were 96.53% and 12.64 g/g, respectively, achieved at optimum factors of Z1 (7.8 g/L), Z3 (3 g), and Z4 (1.18 mm), as well as at Z1 (15.6 g) and Z3 (1 g). The isotherm and kinetic data, respectively, followed the Langmuir isotherms and the pseudo-second-order kinetics with a maximum monolayer biosorptive capacity of 23.31 g g-1. The mechanism of biosorptive crude oil removal was by physical sorption and film diffusion control. Therefore, the maize cob represents an inexpensive and effective natural sorbent for oil spill removal from water bodies.

Effects of antibiotics on corncob supported solid-phase denitrification: Denitrification and antibiotics removal performance, mechanism, and antibiotic resistance genes

Solid-phase denitrification (SPD) has been used in wastewater treatment plant effluent to enhance nitrate removal, and antibiotics co-existing in the effluent is a common environmental problem. In this study, it was systematically investigated the effect of single trace sulfamethoxazole (SMX)/trimethoprim (TMP) and their mixture on microbial denitrification performance, the antibiotics removal, and antibiotics resistance genes (ARGs) in corncob supported SPD system. The average denitrification rate was improved by 46.90% or 61.09% with single 50 µg/L SMX or TMP, while there was no significant inhibition with mixed SMX and TMP. The abundance of dominant denitrifiers (Comamonadaceae family and Azospia) and fermentation bacteria (Ancalomicrobium) were consistent with the denitrification performance of different antibiotics groups. Single SMX and TMP achieved relatively higher denitrification gene and enzyme abundance. Mixed SMX and TMP improved the denitrification gene copies, but they reduced the key denitrification enzymes except for EC 1.7.7.2. Additionally, the removal efficiency of TMP (56.70% ± 3.18%) was higher than that of SMX (25.44% ± 2.62%) in single antibiotic group, and the existence of other antibiotics (i.e. SMX or TMP) had no significant impact on the TMP or SMX removal performance. Biodegradation was the main removal mechanism of SMX and TMP, while sludge and corncob adsorption contributed a little to their removal. SMX had the risk of sulfanilamide resistance genes (SRGs) dissemination. Furthermore, network analysis indicated that Niveibacterium and Bradyrhizobium were the potential hosts of SRGs, which promoted the horizontal transmission of ARGs.

Sustainable robust green synthesis of nanoparticles from waste aquatic plants and its application in environmental remediation

Green synthesis of nanoparticles using natural materials is an emerging technique that fascinates the scientific community globally for the treatment of wastewater. In the present study, aquatic plants such as Piaropus crassipes (PC) and Lemna gibba (LG), were utilized to make low-cost nanoparticles, and its feasibility for the removal of Zn(II) ions was studied. The synthesized nano adsorbents were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and zeta potential analysis. The optimal conditions were evaluated by batch adsorption studies, to investigate the parameters such as pH (2-7), adsorbent dosage (0.5-5 g/L), initial concentration (20-60 mg/L), and contact time (10-120 min) etc. The isotherm, and kinetic data results fit well with Langmuir, and pseudo-second order models. The anticipated monolayer adsorption capacity with respect to the PC, and LG was found to be 42.41 mg/g and 27.65 mg/g, respectively. Thermodynamic studies showed that the process is exothermic. The adsorption mechanism of PC/LG on Zn(II) exhibited surface complexation, ion exchange, and diffusion. Desorption studies were performed to analyze the recovery potential of Zn(II) ion. Hence, this article investigates the economic synthesis of green nanoparticles, and their potential utilization in heavy metal remediation.

Mathematical modeling and numerical simulation of sulfamethoxazole adsorption onto sugarcane bagasse in a fixed-bed column

Having rigorous mathematical models is essential for the design and scaling of adsorption columns. In this study, the dynamic behavior of the sulfamethoxazole adsorption on sugarcane bagasse was studied and compared using analytical models and a theoretical mechanistic model. Initially, fixed-bed column tests were carried out at different flow rates and bed heights. Then, the experimental data were fitted with the most widely used analytical kinetic models, and their fit and fixed-bed parameters were compared with the mechanistic model. Of all analytical models analyzed, the Log-Gompertz model was the one that had the best agreed with experimental data. Although some analytical models fitted the experimental data accurately, their usefulness was questionable. Their parameters did not show a clear relationship with the change in operating conditions, and in certain cases had different behavior from that observed in experimentation. Conversely, the mechanistic model not only predicted the breakthrough curves with great accuracy in the initial and transition stage (R² > 0.92; SSE < 0.06), but it also estimated relevant parameters. Additionally, the effects of the global mass transfer coefficient (K_i) and the axial dispersion coefficient (D_z) on breakthrough curves were studied using the mechanistic model. Increasing K_i increased the slope of the breakthrough curves with a faster adsorption rate. Similarly, high values of D_z produced lower adsorption capacities of the adsorbent; and it was established that the axial dispersion is relevant in SMX adsorption on SB. The theoretical model presented can be used for the design, scaling, and optimization of adsorption columns.

Mechanistic insights into the adsorption of methylene blue by particulate durian peel waste in water

This study aims to investigate the adsorption of methylene blue (MB) over particulate durian peel waste, which is chemically activated with hydrogen peroxide. The equilibrium data are well described by the Freundlich isotherm model, which indicates that the MB adsorption takes place predominantly on multilayers and heterogeneous surfaces of the biosorbent. The Freundlich adsorption constants, K_F and n, are 11.06 L/g and 2.94, respectively. Thermodynamic data suggest that the MB adsorption occurs spontaneously and endothermically. The enthalpy and entropy for the MB adsorption are obtained as 10.26 kJ/mol and 0.058 kJ/mol K, respectively, in the temperature range of 303-323 K. Based on the stepwise desorption method, the adsorption of MB is dominated by physical interactions, particularly hydrogen bonding.

Assessment of Untreated Coffee Wastes for the Removal of Chromium (VI) from Aqueous Medium

Industrial discharges loaded with heavy metals present several problems for aquatic ecosystems and human health. In this context, the present study aims to evaluate the potential of raw spent coffee grounds to remove chromium from an aqueous medium. A structural and textural study of coffee grounds was carried out by FTIR, XRD, and TGA analysis. The optimum conditions for the removal of Cr(VI), for a solution with an initial concentration of 100 mg/l, were adsorbent dose 2.5 g/l, pH 4.0, and contact time 90 min. The adsorption equilibrium results show that the Langmuir isotherm best describes the process with an adsorption capacity of 42.9 mg/g and that the adsorption kinetics follows the pseudosecond-order model. The calculated thermodynamic parameters showed that the adsorption is exothermic and spontaneous. The activation energy value (Ea) indicated that the retention is physisorptive in nature. The regeneration of the adsorbent was carried out by three eluents, among which HCl was the best. Finally, a brief cost estimation showed the great potential of coffee grounds as a low-cost adsorbent.