Amoxicillin removal from water by adsorption on activated carbon of mineral sources: discussion of experimental data, mechanisms and modeling

The use of antibiotics has increased considerably in the last decades in human medicine, as well as agriculture and animal production. Consequently, high loads of these emerging contaminants in the environment can increase antibiotic-resistant genes and the development of multi-resistant pathogenic microorganisms. This work aims to evaluate the removal of amoxicillin trihydrate in aqueous medium using mineral-activated carbon of bituminous origin as an adsorbent. The adsorbent was classified as microporous with associated mesopores, showing phenolic groups on its surface, which indicates the versatility of the adsorbent. The adsorption kinetics and isotherms were predominantly chemical. Pseudo-second-order model, as well as LDF model adjusted to the kinetic data. Sips and Langmuir isotherms adjusted to the adsorption equilibrium data. The maximum adsorptive capacity obtained experimentally was 313.30 mg g-1 at 50°C. The thermodynamic properties suggested spontaneous, monolayer, and endothermic adsorption. Overall, compared to previous works, the adsorbent proved to be a viable and promising alternative for the removal of antibiotics from water, with high adsorption capacity of amoxicillin, without being necessary to perform any prior changes to the material.

Electrocoagulation treatment of furniture industry wastewater

Electrocoagulation was investigated as a method for treating wastewater containing polyvinyl acetate (PVAc) from the furniture industry. The study evaluated the evolution of iron concentration and passivation during the treatment process. Laboratory-scale experiments were conducted to evaluate the effects of inter-electrode distance (d), current density, and mode on treatment performance. Three values of d (0.3, 0.6, and 0.9 cm) were studied and found to have no significant effect on performance. However, lower d values resulted in reduced energy consumption due to a decrease in applied voltage. Three values of current density (132, 158, and 197 A m^-2) were studied under two current modes, Direct Current (DC) and Alternating Pulsed Current (APC). The best treatment performance for DC occurred under 158 A m^-2 (the treated wastewater was characterized by pH = 4.59 ± 0.02, conductivity = 996 ± 21 μS cm^-1, COD = 1940 ± 55 mgO₂ L^-1, TSS = 105 ± 14 mg L^-1, and Fe = 50.39 ± 1.87 mgFe L^-1). For APC, the best performance was achieved under 197 A m^-2 (the treated wastewater was characterized by pH = 6.33 ± 0.06, conductivity = 988 ± 17 μS cm^-1, COD = 1942 ± 312 mgO₂ L^-1, TSS = 199 ± 55 mg L^-1, and Fe = 44.68 ± 4.60 mgFe L^-1). Despite the promising results, treatment performance was insufficient to meet the legal requirements for water discharge. APC was found to be a more economically viable approach, as it reduced anode wear, electrode passivation, and energy consumption. The quantity of iron released increased with d, and the effect of current density on iron concentration was found to be non-linear. However, applying APC reduced the iron content for all tested current densities. The tests showed that EC was effective in removing chemical oxygen demand (COD) and total suspended solids (TSS), achieving removal efficiencies above 92% and 99%, respectively. However, the studied treatment procedures were insufficient to meet the EU legal requirements for water discharge. Therefore, the obtained wastewater should undergo a post-treatment process.

The role of the current waveform in mitigating passivation and enhancing electrocoagulation performance: A critical review

Electrocoagulation (EC) can be an efficient alternative to existing water and wastewater treatment methods due to its eco-friendly nature, low footprint, and facile operation. However, the electrodes applied in the EC process suffer from passivation or fouling, an issue resulting from the buildup of poorly conducting materials on the electrode surface. Indeed, such passivation gives rise to various operational problems and restricts the practical implementation of EC on a large scale. Therefore, it has been suggested that using pulsed direct current (PDC), alternating pulse current (APC), and sinusoidal alternating current (AC) waveforms in EC as alternatives to conventional direct current (DC) can help mitigate passivation and alleviate its associated detrimental effects. This paper presents a critical review of the impact of the current waveform on the EC process towards the capabilities of the PDC, APC, and AC waveforms in de-passivation and performance enhancement while comparing them to the conventional DC. Additionally, current waveform parameters influencing the surface passivation of electrodes and process efficiency are elaborately discussed. Meanwhile, the performance of the EC process is evaluated under different current waveforms based on pollutant removal efficiency, energy consumption, electrode usage, sludge production, and operating cost. The proper current waveforms for treating various water and wastewater matrices are also explained. Finally, concluding remarks and outlooks for future research are provided.

Removal of nutrients and other emerging inorganic contaminants from water and wastewater by electrocoagulation process

The continual discharge of emerging inorganic pollutants into natural aquatic systems and their negative effects on the environment have motivated the researchers to explore and develop clean and efficient water treatment strategies. Electrocoagulation (EC) is a rapid and promising pollutant removal approach that does not require any chemical additives or complicated process management. Therefore, inorganic pollutant treatment via the EC process is considered one of the most feasible processes. The potential developments of EC process may make the process a wise choice for water treatment in the future. Thus, the present study mainly focuses on the use of EC technology to remove nutrients and other emerging inorganic pollutants from water medium. The operating factors that influence EC process efficiency are explained. The major advancement of the EC technique as well as field-implemented units are also discussed. Overall, this study mainly focuses on emerging issues, present advancements, and techno-economic considerations in EC process.

Optimal setting strategy of electrocoagulation process in heavy metal wastewater treatment plant

With the increasingly stringent environmental protection policies of various countries, the contradiction between the treatment cost and the purification degree of environmental pollutants has become increasingly significant, which has become a major factor restricting the efficient operation of wastewater treatment plants. Hence, keeping the ion concentration at the outlet as low as possible while reducing the cost are the main objectives of treating heavy metal wastewater by electrocoagulation (EC) process. However, due to the complicated mechanism and uncertain production conditions, it is difficult to achieve those goals by manually setting the current through operators' experience. In this paper, we develop a dynamic multi-objective optimization strategy for EC process to balance these two conflicting production targets. First, we define the removal efficiency (RE) to measure the effectiveness of the EC process. Due to the anodic passivation and cathodic polarization in the EC process, the current reversing period (CRP) is proposed and optimized to ensure the stable performance of the electrodes. Then the current setting problem is formulated as a constrained multi-objective optimization problem with competing objectives of RE and cost. An interval-adjustable control parameterization (CP) approach is developed to reduce the complexity of this optimization problem. To compute this optimization problem, a heuristic method named multi-objective state transition algorithm (MOSTA) with evaluation value is investigated. The effectiveness of our model and optimization strategy is demonstrated by a successful implementation in an EC process of a wastewater treatment plant in Chenzhou, China.

Evaluation of energy and electrode consumption of Acid Red 18 removal using electrocoagulation process through RSM: alternating and direct current

This study aims to evaluate energy and electrode consumption for Acid Red 18 (AR18) removal and the operating costs employing alternating current (AC) and direct current (DC) in an electrocoagulation (EC) system. As the novelty of this study, the effects of AC/DC mode and electrode type were scrutinized through a series of designed experiments in a batch EC reactor to remove a globally used Azo dye from wastewater. In this regard, by designing the experiments with response surface methodology (RSM), four series of 30 experiments were separately conducted employing DC and AC for iron (Fe) and aluminum (Al) electrodes. In each series, quadratic models were achieved for the removal efficiency and operating costs; by confirming the accuracy of the models, two responses were simultaneously optimized accordingly. As a result, the AR18 removal efficiency with Al electrodes had no significant difference using AC and DC (on average 0.2% difference); however, for Fe electrode, the EC performance in DC was more significant than AC (on average 13.8% difference). Also, the operating costs of Fe electrode were more economical in comparison with the Al; on average, the operating costs in the case of applying DC for Fe and Al were achieved 14.6 and 39.8 (US$/kg dye removed), respectively; whereas, for AC, this amount was calculated 9.3 and 36.0 (US$/kg dye removed) for Fe and Al, respectively.

Optimization of the electrochemical reduction process and ORP effects in nitrate removal

Nitrate contaminated water resources, a huge environmental problem for countries, including our own. This research aims to evaluate the efficiency of the electrochemical process for the removal of nitrate from the aqueous solution by direct and alternating current. Experiments were done by the Taguchi method, including electrode array, time exposure, voltage, pH, and the initial concentration of nitrate. Minitab 17 and SPSS 18 software were utilized to design and data analysis. In detail, the connection of the electrodes was monopolar, and the direct current (DC) has a greater efficiency as alternating current (AC) in the nitrate removal (p > 0.001). In AC, the nitrate initial concentration, voltage, electrodes material, contact time, and pH have the most effect on the nitrate removal. The optimized conditions for nitrate removal include Al-Al electrode, pH of 7, a voltage of 30 V, and nitrate initial concentration of 100 mg/L with the contact of time 150 min. Selection of appropriate materials for electrodes construction, adequate voltage, and removal of intervention agents from aqueous solution led to greater removal efficiencies. The optimized conditions that can reduce the aqueous solution ORP with high speed and the electrochemical reactor efficiency for nitrate removal were increased. PRACTITIONER POINTS: Electrochemichal (EC) process is evaluated for treatment of nitrate wastewater for the first time. High removal efficiency (over 95%) from nitrate wastewater was obtained. Minimizing energy consumption and maximizing nitrate removal were simultaneously achieved in the integrated single EC process.

Study on highly efficient Cr(VI) removal from wastewater by sinusoidal alternating current coagulation

Cr(IV) pollution in water leads to serious environmental contamination and health risks. Among various wastewater treating methods, electrocoagulation (EC) is widely applied because of its high efficiency. However, there is still a problem of high energy consumption that has to be solved by direct current coagulation (DCC). In this paper, a sinusoidal alternating current coagulation (SACC) technique was used to reduce energy consumption and improve the efficiency of Cr(VI) removal. The effects of pH value, current density, initial concentration of Cr(VI) and reaction time are studied on the removal of Cr(VI). The response surface methodology (RSM) was used to optimize the parameters of SACC process. Compared with pulse direct current coagulation (PDCC) and DCC, SACC can greatly reduce the concentration polarization and prevent Fe electrodes from passivation so as to reduce energy consumption and improve the efficiency of Cr(VI) removal. When pH 5.6 wastewater containing 33.1 mg⋅dm^-3 Cr(VI) was treated by applying 2.7 A⋅m^-2 density for 20.5 min, the removal rate of Cr(VI) reached 99.73%, and the residual Cr(VI) in the effluent was <0.1 mg⋅dm^-3. The power consumption of SACC process decreases by 14.98% compared to DCC process and the electrode loss is about 16.4% less than that of the DCC. The coagulation produced by SACC has a large specific surface area and better adsorption performance through analysis of SEM and EDS as well as adsorption dynamic analysis. FTIR and XRD patterns verified the strong interaction between Cr(VI) and iron sol. The Cr(VI) on the electrode can be deposited as a form of insoluble Cr(III) compounds. Langmuir adsorption isotherm model and the second-order kinetic model in SACC are more suitable to explain the adsorption behavior and characteristics of Cr(VI) in SACC.

Decomposition of Bis(N-benzyl-salicydenaminato)zinc (II) Complex for the Synthesis of ZnO Nanoparticles to Fabricate ZnO-Chitosan Nanocomposite for the Removal of Iron (II) Ions from Wastewater

The whole world is faced with a huge challenge of the shortage of clean water due to industrialization and the intimidation of climate change. Poor water quality distresses many areas of human’s well-being. Although there are existing technologies for water treatments, many of these methods utilize toxic substances which create more problems into the environment. The preparation of bis(N-benzyl-salicydenaminato)zinc (II) complex and the synthesis of zinc oxide nanoparticles via the thermal decomposition of zinc complex together with the fabrication of ZnO-chitosan nanocomposites for the removal of iron (II) ions from wastewater is reported. The optical properties of the synthesized nanoparticles showed band edges that are red-shifted in wavelengths when the decomposition temperature was increased. The XRD patterns displayed the hexagonal ZnO phase for the synthesized nanoparticles. TEM images revealed spherical-shaped particles which became agglomerated when the temperature was increased. The parameters such as pH, contact time, and initial concentration were investigated during the water treatment. The pH = 6 was found to be optimum, and the highest percentage removal was recovered after three hours for both adsorbents.

Treatment of highly toxic cardboard plant wastewater by a combination of electrocoagulation and electrooxidation processes

The objective of this study was to investigate the removal efficiencies of the electrochemical treatment systems as an alternative for the treatment of cardboard plant wastewater (CPW). In accordance with this purpose, CPW was treated by electrocoagulation (EC) with Al electrodes and the effects of current density (CD), operating time (t), and initial pH (pH_i) were investigated. The results showed that EC at optimum treatment conditions (CD: 7.5mA/cm², pH_i: 7.0 and t: 60min) have limited removal efficiencies for total organic carbon (TOC; 17.1%) and chemical oxygen demand (COD, 14.2%), on the contrary of turbidity (98.7%). Due to the low TOC and COD removal efficiencies, a secondary treatment was needed and the electrocoagulated effluent was subjected to electrooxidation (EO) by using a boron doped diamond (BDD) electrode for investigating the effect of CD, t, pH_i and electrolyte concentration (C_e). Higher TOC (83.7%) and COD (82.9%) removal efficiencies were obtained by EO under the optimum treatment conditions (CD: 100mA/cm², pH_i: 7.2, C_e: 5.0g/L Na₂SO₄ and t: 180min). In addition, a toxicity test was carried out to the raw and treated wastewater under the optimum operating conditions. This study demonstrated that the combination of EC and EO have a satisfactory potential for real industrial wastewater with a high organic content, suspended solids and toxicity.

Arsenic removal by electrocoagulation process: Recent trends and removal mechanism

Arsenic contamination in drinking water is a major issue in the present world. Arsenicosis is the disease caused by the regular consumption of arsenic contaminated water, even at a lesser contaminated level. The number of arsenicosis patients is increasing day-by-day. Decontamination of arsenic from the water medium is the only one way to regulate this and the arsenic removal can be fulfilled by water treatment methods based on separation techniques. Electrocoagulation (EC) process is a promising technology for the effective removal of arsenic from aqueous solution. The present review article analyzes the performance of the EC process for arsenic removal. Electrocoagulation using various sacrificial metal anodes such as aluminium, iron, magnesium, etc. is found to be very effective for arsenic decontamination. The performances of each anode are described in detail. A special focus has been made on the mechanism behind the arsenite and arsenate removal by EC process. Main trends in the disposal methods of sludge containing arsenic are also included. Comparison of arsenic decontamination efficiencies of chemical coagulation and EC is also reported.

Low-energy hydraulic fracturing wastewater treatment via AC powered electrocoagulation with biochar

Produced and flowback waters are the largest byproducts associated with unconventional oil and gas exploration and production. Sustainable and low cost technologies are needed to treat and reuse this wastewater to avoid the environmental problems associated with current management practices (i.e., deep well injection). This study presents a new process to integrate AC-powered electrocoagulation (EC) with granular biochar to dramatically reduce energy use and electrode passivation while achieving high treatment efficiency. Results show achieving a 99% turbidity and TSS removal for the AC-EC-biochar system only used 0.079 kWh/m(3) or 0.15 kWh/kg TSS, which is 70% lower than traditional DC-EC systems and orders of magnitude lower than previous studies. The amount of biochar added positively correlates with energy saving, and further studies are needed to improve organic carbon and salt removal through system integration.