Chromium removal and water recycling from electroplating wastewater through direct osmosis: Modeling and optimization by response surface methodology

Background: Considering the carcinogenic effects of heavy metals, such as chromium, it is essential to remove these elements from water and wastewater. Direct osmosis is a new membrane technology, which can be a proper alternative to conventional chromium removal processes. Methods: The wastewater samples were collected from an electroplating unit, located in Alborz industrial city, Qazvin, Iran. Magnesium chloride was used as the draw solution, and a semipermeable membrane (Aquaporin) was used in this study. The experiments were designed, using response surface methodology (RSM) and central composite design (CCD) with draw solution concentration (0.5- 1.5 M), feed solution concentration (4-12 mg/L), and experiment time (30-90 minutes) as variable factors. The chromium concentration and water flux were also measured, based on atomic absorption spectrophotometry and water flux equation, respectively. Results: Direct osmosis was highly efficient in chromium removal and water recycling. Water flux and chromium removal efficiency were 15.6 LMH and 85.58%, respectively, under optimal conditions (draw solution = 1.27 mol/L, feed solution = 4 mg/L, and experiment time = 90 min). In terms of validity, the results predicted by the quadratic polynomial model were in good agreement with the responses reported in the laboratory. Conclusion: In direct osmosis, the use of magnesium chloride as the draw solution resulted in the acceptable chromium removal from electroplating wastewater. Using this method, chromium concentration in wastewater reduced to a level lower than the discharge standards, established by Iran’s Department of Environment. Keywords: Direct osmosis, Chromium removal, Electroplating, Optimizatio

Effective removal of Hg2+ from aqueous solutions and seawater by Malva sylvestris

This paper introduces a biomaterial prepared from Malva sylvestris for environmental remediation and medicine treatment purposes. The effects of pH (2–12), adsorbent dose (0.1–1.25 mg/L), Hg2+ concentration (5–15 mg/L), and contact time (3–60 min) were studied on the removal of Hg2+ from aqueous phase. The results were compared with powder of charcoal tablet, a medicine drug. At pH solution of 8, over 96% removal of 10 mg/L Hg2+ was obtained for a M. sylvestris powder (MSP) dose of 1.5 mg/L after a 40 min contact time; while for these conditions only 60% of Hg2+ was removed by charcoal tablet powder (CTP). The Langmuir model was the best fit for the experimental data, which attains a maximum adsorption capacity of 602 and 389 mg/g for MSP and CTP, respectively. Surface analyses (Fourier transform infrared, scanning electron microscopy, Brunauer, Emmet, and Teller, and X-ray photoelectron spectroscopy) of the MSP were also performed. The co-adsorption study indicated that the Hg2+ adsorption by MSP was 33% increased by addition of 2 mg/L ceftriaxone antibiotic. The MSP had acceptable performance after four times recycling. The MSP could be used to remove Hg2+ ions from seawater. Accordingly, the finding of this work suggests that the prepared adsorbent, MSP, is an efficient, no-cost, and promising biomaterial for the removal of Hg2+ ion from liquid phase and could be substituted for charcoal tablets in medicine

Optimization of the Forward Osmosis Process Using Aquaporin Membranes in Chromium Removal

Due to the lack of affordable and feasible wastewater treatment technologies, various industries in developing countries are discharging chromium (Cr) without meeting the environmental standards. Here, the aim was to employ forward osmosis (FO) using aquaporins (AQP)‐based biomimetic membranes and optimize the Cr rejection through response surface methodology (RSM). The initial concentration of draw solution, feed solution, and time was selected as independent variables in order to optimize Cr rejection and water flux. A high Cr rejection efficiency and water flux were achieved under the optimal conditions. These results revealed that the FO process applying an AQP membrane beside the RSM could be considered to treat wastewaters containing heavy metals

Application of oak powder/Fe 3 O 4 magnetic composite in toxic metals removal from aqueous solutions

In this study, the capability of a magnetic composite of oak powder/Fe 3 O 4 (OP/Fe 3 O 4 ) for the adsorption of lead, cobalt, and nickel ions from aqueous solutions was examined. Characteristics and structure of oak powder (OP) and OP/Fe 3 O 4 magnetic composite were explored by FTIR, SEM, TGA-DTG, VSM, and XRD analysis. The XRD results showed that OP/Fe 3 O 4 magnetic composite and OP were in crystalline form. Kinetic behavior of adsorption process was studied using pseudo-first-order, pseudo-second-order, and Elovich models. Results indicated that the pseudo-second-order model (R 2 > 0.999) can better describe the kinetic behavior of the metal adsorption process. Equilibrium behavior of the adsorption process was also tested using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Scatchard isotherm models. The results revealed that the adsorption equilibrium data for three metals match with the Freundlich isotherm model (R 2 > 0.99). This indicates the effectiveness of heterogeneous surfaces in comparison with homogeneous ones in the adsorption process of metal ions. Moreover, the results showed that the adsorption process of metal ions with the OP/Fe 3 O 4 magnetic composite is physical. Finally, negative values of enthalpy and entropy indicated that the process of the metal ion adsorption is spontaneous and exothermic

Developing a Thin Film Composite Membrane with Hydrophilic Sulfonated Substrate on Nonwoven Backing Fabric Support for Forward Osmosis

This study describes the fabrication of sulfonated polyethersulfone (SPES) as a super-hydrophilic substrate for developing a composite forward osmosis (FO) membrane on a nonwoven backing fabric support. SPES was prepared through an indirect sulfonation procedure and then blended with PES at a certain ratio. Applying SPES as the substrate affected membrane properties, such as porosity, total thickness, morphology, and hydrophilicity. The PES-based FO membrane with a finger-like structure had lower performance in comparison with the SPES based FO membrane having a sponge-like structure. The finger-like morphology changed to a sponge-like morphology with the increase in the SPES concentration. The FO membrane based on a more hydrophilic substrate via sulfonation had a sponge morphology and showed better water flux results. Water flux of 26.1 L m−2 h−1 and specific reverse solute flux of 0.66 g L−1 were attained at a SPES blend ratio of 50 wt % when 3 M NaCl was used as the draw solution and DI water as feed solution under the FO mode. This work offers significant insights into understanding the factors affecting FO membrane performance, such as porosity and functionality

Characteristics and performance of Cd, Ni, and Pb bio-adsorption using Callinectes sapidus biomass: real wastewater treatment

In the current study, the bio-adsorption potential of Callinectes sapidus biomass for control of cadmium, nickel, and lead from the aqueous stream was assessed. Spectrum analysis of FTIR, AFM, EDAX, mapping, SEM, TEM, and XRF was used to study the properties of the C. sapidus biomass. The XRF analysis revealed that C. sapidus bio-adsorbent has various effective metal oxides that can be useful to adsorb pollutants. The best model to describe the equilibrium data was Freundlich isotherm. The Langmuir bio-adsorption capacity was reported at 31.44 mg g −1 , 29.23 mg g −1 , and 29.15 mg g −1 for lead, cadmium, and nickel ions, respectively. Pseudo-first-order and pseudo-second-order kinetic models were studied to test the kinetic behavior of the process. An intra-particle diffusion model was used to determine the effective mechanisms involved in the bio-adsorption. Based on t 1/2 , it can be concluded that the equilibrium speed of the bio-adsorption process is high. The thermodynamic study showed that the metal bio-adsorption process using C. sapidus biomass is exothermic and spontaneous. The field applicability of the crab bio-adsorbent for eliminating concurrently several contaminants (metal ions, antibiotics, sulfate, nitrate, and ammonium) from an actual wastewater was successfully examine

Cyanide adsorption from aqueous solution using mesoporous zeolite modified by cetyltrimethylammonium bromide surfactant

The purpose of this study was the modification of zeolite with the cationic surfactant of cetyltrimethylammonium bromide for enhancing the adsorption of cyanide (CN−) from aqueous solution. Hence, the batch tests were conducted under different conditions for CN− removal by the surfactant-modified zeolite (SMZ). The effect of pH (3–10), SMZ dosage (0.25–5 g/L), CN− concentration (50, 100, and 200 mg/L), and contact time (5–400 min) was evaluated. More than 95% of cyanide was removed at the conditions of pH of 10, the initial cyanide concentration of 100 mg/L, the SMZ dosage of 4 g/L, and the contact time of 250 min. The analysis of kinetics adsorption showed that cyanide ions adsorption onto the SMZ clearly followed the pseudo-second-order model. The isotherm adsorption data were mostly matched by Langmuir model with maximum adsorption capacity of 49.57 mg/g. The fresh and used SMZ was fully characterized by Brunauer–Emmett–Teller, Barrett–Joyner–Halenda, loss of ignition, X-ray powder diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, and pH of zero point charge (pHzpc). The surface study indicated that the adsorbent is mesoporous and crystalline. The adsorption–desorption study was done using three reagents of HNO3, HCl, and NaOH. A metal plating wastewater was successfully treated using SMZ. Accordingly, the SMZ was found to be an effective adsorbent for the removal of different concentrations of cyanide from aqueous solution

Monitoring and eco-toxicity effect of paraben-based pollutants in sediments/seawater, north of the Persian Gulf

The current work is documented as the first record of the characteristics, removal efficiency, partitioning behavior, fate, and eco-toxicological effects of paraben congeners in a municipal wastewater treatment plant (WWTP, stabilization ponds) and hospital WWTPs (septic tank and activated sludge), as well as seawater-sediments collected from runoff estuarine stations (RES) and coastal stations (CS) of the north of the Persian Gulf. The median values of Σparabens at the raw wastewater and effluent of the studied WWTPs were 1884 ng/L and 468 ng/L, respectively. The activated sludge system had a greater removal efficiency (56.10%) in removing ∑parabens than the septic tank (45.05%) and stabilization pond (35.54%). The discharge rates of methyl paraben (MeP) was computed to be 2.23, 21.18, and 9.12 g/d/1000 people for stabilization ponds, septic tank, and activated sludge, respectively. Median concentrations of Σparabens in seawater (103.42 ng/L) and sediments (322.05 ng/g dw) from RES stations were significantly larger than from CS stations (61.2 and 262.0 ng/g dw in seawater and sediments, respectively) (P < 0.05). The median of field-based koc for Σparabens was 130.81 cm3/g in RES stations and 189.51 cm3/g in CS stations. It was observed that the concentration of parabens could have negative impacts on some living aquatic populations (invertebrates and bacteria), but the risk was not significant for fishes and algae