Energy production from treatment of industrial wastewater and boron removal in aqueous solutions using microbial desalination cell

Performance of microbial desalination cells with different cathode types in treating saline wastewater

Microbial desalination cells (MDCs), as an emerging desalination technology, have attracted increasing attention in recent years due to their ability to simultaneously achieve salt removal and wastewater treatment without the need for external energy input. In this study, the performance of two MDC systems with different cathode types-a biocathode (MDC1#) and a permanganate cathode (MDC2#)-was comparatively evaluated for the treatment of saline wastewater, with a particular focus on voltage output, desalination efficiency, and chemical oxygen demand (COD) removal. Experimental results showed that the average output voltage of MDC2# reached 742.02 mV, which was significantly higher than that of MDC1# (695.6 mV). Its maximum power density was as high as 6.22 W/m3, approximately six times that of MDC1#. Moreover, MDC2# exhibited a higher average chloride removal rate in the desalination chamber (32.34 mg/h), compared to 17.13 mg/h for MDC1#, indicating superior desalination performance. However, in terms of electron recovery, MDC1# achieved a much higher average Coulombic efficiency (28.8 ± 18.7%), nearly three times that of MDC2#, suggesting more efficient electron utilization with the biocathode. Regarding ammonium removal, MDC1# demonstrated a higher initial removal efficiency within the first 96 h (74.3%, with an average rate of 4.17 mg/h), but this declined sharply over time, with the later-stage rate dropping to only 0.32 mg/h (less than 10% of the initial rate). In contrast, MDC2# maintained a relatively stable ammonium removal rate throughout the operation (ranging from 0.58 to 3.27 mg/h, with an average of 1.92 mg/h). In addition, both systems achieved stable COD removal at the anode, with efficiencies consistently above 85%. Overall, the permanganate cathode is more suitable for applications that require high voltage output and efficient desalination, whereas the biocathode shows significant advantages in organic pollutant removal and energy recovery. This study provides a theoretical foundation for the rational selection of cathode types based on the characteristics of saline wastewater, offering valuable guidance for optimizing MDC system performance.

Heterogeneous electro-Fenton treatment of coking wastewater using Fe/AC/Ni cathode: optimization of electrode and reactor organic loading

A self-developed iron-loaded activated carbon-based nickel foam electrode (Fe/AC/Ni cathode) was used to construct electro-Fenton reaction system to treat coking wastewater. To meet the gap between laboratory beaker experiments and field trials for practical applications, we proposed and validated a method for obtaining organic loads, the essential parameters used in the design of electrochemical systems for wastewater treatment. The three influencing factors most relevant to organic loading, the effective surface area of cathode, chemical oxygen demand (COD) concentration of influent, and treatment time, were selected and investigated for their effects on the COD removal rate of coking wastewater by single-factor experiments and further optimized by response surface method. The appropriate electrode area load (La) and reactor volume load (Lv) were calculated by their corresponding intrinsic relationships with the three factors. The optimum application conditions were effective surface area of cathode 28.5 cm2, COD concentration of influent 1.76 kg·m-3, and treatment time 160.43 min. Under these conditions, the maximum COD removal rate was 98.51%. The La and Lv were 8.905 mgCOD·cm-2·h-1 and 0.634 kgCOD·m-3·h-1, respectively. The characterization experiment results showed that the Fe/AC/Ni cathode had a significant effect on the treatment of refractory organic contaminants in coking wastewater.

Recent advances in boron removal in aqueous media. An approach to the adsorption process and process optimization

The numerous oxidation states of the element boron bring great challenges in containing its contamination in receptor bodies. This scenario increases significantly due to the widespread use of boron compounds in various industries in recent years. For this reason, the removal of this contaminant is receiving worldwide attention. Although adsorption is a promising method in boron removal, finding suitable adsorbents, that is, those with high efficiency, and feasible remains a constant challenge. Hence, this review presents the boron removal methods in comparison to costs of adsorbents, reaction mechanisms, economic viability, continuous bed application, and regeneration capacity. In addition, the approach of multivariate algorithms in the solution of multiobjective problems can enable the optimized conditions of dosage of adsorbents and coagulants, pH, and initial concentration of boron. Therefore, this review sought to comprehensively and critically demonstrate strategic issues that may guide the choice of method and adsorbent or coagulant material in future research for bench and industrial scale boron removal.

Microbial desalination cell treated spent geothermal brine as a nutrient medium in hydroponic lettuce cultivation: Health risk assessment

The scarcity and contamination of freshwater resources are extremely critical issues today, and the expansion of water reuse has been considered as an option to decrease its impact. Therefore, the reuse of microbial desalination (MDC)-treated spent geothermal brine for agricultural purposes arises as a good solution to prevent water contamination and provide sustainable water usage. In this study, the potential of treated spent geothermal water from MDC system as a nutrient solution for the hydroponic cultivation of lettuce was evaluated. The effects of different water samples (Hoagland solution (R1) as a control, MDC-treated water (R2), 1:1, v/v mixture of MDC-treated water and Hoagland solution (R3), 4:1, v/v mixture of MDC-treated water and Hoagland solution (R4), and tap water (R5)) on lettuce growth were considered. The application of R3 and R4 samples for hydroponic lettuce cultivation was promising since the lettuce plants uptake sufficient nutrients for their growth and productivity with low toxic metal concentrations. In addition, the chlorophyll-a, chlorophyll-b, and carotene contents of lettuce were in the range of 1.045-2.391 mg/g, 0.761-1.986 mg/g, and 0.296-0.423 mg/g in different water samples, respectively. The content of chlorophyll-a was highest in R1 (2.391 mg/g), followed by R3 (2.371 mg/g). Furthermore, the health risk assessment of heavy metal accumulations in the lettuce plants cultivated in the various water samples was determined. Results showed that heavy metal exposure via lettuce consumption is unlikely to suffer noticeable adverse health problems with values below the permissible limit value.

An integrated MDC-FO membrane configuration for simultaneous desalination, wastewater treatment and energy recovery

A novel microbial desalination cell (MDC) configuration was developed by introducing a forward osmosis (FO) membrane, separating the cathode chamber from a fourth extra chamber. Wastewater is treated using a sequential anode-cathode feed. The new chamber then serves as a FO draw chamber, where a saline solution is used to recover freshwater from the adjacent cathode chamber. The diluted saline solution then goes to the MDC middle chamber for further desalination. Three identical cells were constructed and operated in cyclic-batch-flow mode at different initial wastewater and saline solution concentrations. Up to 84.8 ± 1.7% of the wastewater was recovered as freshwater. Freshwater recovery decreases at lower salt concentrations and higher wastewater COD concentrations due to the lower osmotic pressure difference. Salinity of saline water was decreased by up to 69.57 ± 3.85% at the highest initial salinity. COD removal up to 94.42 ± 4.15% was reached. COD removal rates were higher at higher COD concentrations. Polarization curves show the effect of COD on the internal resistance, where cells operated at lower COD experienced higher internal resistance. Scanning electron microscopy (SEM) images revealed the extent of fouling on the ion exchange membrane and biofilm formation on the FO membranes and the electrodes.

Identifying Geogenic and Anthropogenic Aluminum Pollution on Different Spatial Distributions and Removal of Natural Waters and Soil in Çanakkale, Turkey

The Çanakkale-Kirazlı region (Turkey) is enriched with minerals, especially aluminum (Al), which dangerously get transported into aquatic media due to several mining and geological activities in recent years. In this study, Al and other potentially toxic metals (PTMs) including B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Si, and Zn, in both water and soil samples, were measured for quality determination. Selected metals were also analyzed by the enrichment factor (EF), the geoaccumulation index (I _geo), the contamination factor (CF), and the pollution load index (PLI) to evaluate both water and soil pollution geogenically or anthropogenically. Also, the metals were clustered to support the pollution source with Pearson's correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA). Forty-five natural water samples and 12 soil samples were collected spatially. To perform pollution assessment, two fundamental treatment processes to remove Al pollution from the sample including the highest Al concentration (38.38 mg/L) in water were applied: (1) precipitation with pH adjustment and (2) removal with ion exchange. The pH values of water samples were changed in the range of 3-9 to test the dissolution of Al. The results demonstrated that the study area was mostly under the influence of geogenic aluminum pollution.

Advances in preparation, mechanism and applications of various carbon materials in environmental applications: A review

Carbon-related materials are now widely investigated in a various industrial field due to their excellent and unique qualities. It must be tailored to the application in such a way that it fits the application. At the same time, it needs to be generated in sufficient quantities for commercial use, and the synthesis method is the major sticking point here. Because most new materials are discovered by chance, the synthesis process described here may not be the most effective way to create them. The research is merely a steppingstone to discovering a different approach, and it will continue until the substance is no longer being used. If you're developing materials for any purpose, synthesis processes are essential. Fullerene, carbon nanotubes (CNT), graphene, and MXene are only a few of the carbon-based compounds discussed in this overview study, which also gives a brief prognosis on the materials future. Furthermore, the environmental application of these carbon materials was discussed and commented.

A review of boron removal from aqueous solution using carbon-based materials: An assessment of health risks

Carbon-based compounds have gained attention of researchers for use in boron removal due to their properties, which make them a viable and low cost adsorbent with a high availability, as well as environmental friendliness and high removal efficiency. The removal of boron utilizing carbon-based materials, including activated carbon (AC), graphene oxide (GO), and carbon nanotubes (CNTs), is extensively reviewed in this paper. The effects of the operating conditions, kinetics, isotherm models, and removal methods are also elaborated. The impact of the modification of the lifetime of carbon-based materials has also been explored. Compared to unmodified carbon-based materials, modified materials have a significantly higher boron adsorption capability. It has been observed that adding various elements to carbon-based materials improves their surface area, functional groups, and pore volume. Tartaric acid, one of these doped elements, has been employed to successfully improve the boron removal and adsorption capabilities of materials. An assessment of the health risk posed to humans by boron in treated water utilizing carbon-based materials was performed to better understand the performance of materials in real-world applications. Furthermore, the boron removal effectiveness of carbon-based materials was evaluated, as well as any shortcomings, future perspectives, and gaps in the literature.

Boron removal from aqueous solutions by chitosan/functionalized-SWCNT-COOH: Development of optimization study using response surface methodology and simulated annealing

Boron contamination in water resources (especially drinking waters and agricultural land) is a major problem for the ecosystem. In this study, a novel synthesized chitosan/functionalized-SWCNT-COOH was prepared to separate boron (as boric acid) from aqueous solutions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis revealed that SWCNT was dispersed in chitosan homogenously. Moreover, this study has related to the constrained optimization problem with an engineering approach. Response surface method (RSM) with face-centered central composite design (FCCCD) was chosen for maximizing the adsorption capacity as well as determining optimal independent factors such as pH, adsorbent dose, and concentration of boric acid. The optimized response (adsorption capacity) was reached 62.16 mg g^-1 under the optimal conditions (98.77 mg L^-1 of boric acid concentration, pH of 5.46 and 76 min). The present study has indicated that the synthesized material can be used as an adsorbent for eliminating boric acid from aqueous solutions depending on its high adsorbent capacity to remove boron and has better performance than existing adsorbents. Furthermore, simulated annealing (SA) optimization technique was used to compare the findings of RSM. Moreover, the selected optimization techniques were compared with error functions. The optimal conditions derived from SA were 91.17 mg L^-1 of boric acid concentration, pH of 5.86, and 76.17 min. The optimal adsorption capacity of SA was found to be 62.06 mg g^-1. These results revealed that the predictions of the two models are very close to each other.

Mapping Research on Microbial Fuel Cells in Wastewater Treatment: A Co-Citation Analysis

Microbial fuel cells (MFCs) are promising technologies, aiming at treating different types of industrial and domestic wastewater. In recent years, more and more publications focusing on wastewater treatment have been published. Based on the retrieval of publications from Web of Science Core Collection database, the new emerging trends of microbial fuel cells in wastewater treatment was evaluated with a scientometric analysis method from 1995 to 2020. All publications downloaded from (WOS) were screened by inclusion criteria, and 2233 publications were obtained for further analysis. Document co-citation and burst detection of MFCs in wastewater treatment were analyzed and visualized by software of CiteSpace. Our study indicated that “Environmental Science” is the most popular discipline, while the journal of Bioresource Technology published the greatest quantity of articles in the field of MFCs applied wastewater treatment. China and the Chinese Academy of Science are the most productive country and institution, respectively. “Azo dye” has become the new research topic, which indicates the application area and the development of MFCs. The performance of MFCs for wastewater treatment has been widely discussed. The findings of this study may ameliorate the researcher in seizing the frontier of MFCs in wastewater treatment.