Granular Activated Carbon Adsorption Research Articles

Predicting per‐ and polyfluoroalkyl substances removal in pilot‐scale granular activated carbon adsorbers from rapid small‐scale column tests

AbstractPer‐ and polyfluoroalkyl substances (PFAS) occur widely in drinking water, and consumption of contaminated drinking water is an important human exposure route. Granular activated carbon (GAC) adsorption can effectively remove PFAS from water. To support the design of GAC treatment systems, a rapid bench‐scale testing procedure and scale‐up approach are needed to assess the effects of GAC type, background water matrix, and empty bed contact time (EBCT) on GAC use rates. The overarching goal of this study was to predict PFAS breakthrough curves obtained at the pilot‐scale from rapid small‐scale column test (RSSCT) data. The scale‐up protocol was developed for pilot data obtained with coagulated/settled surface water (TOC = 2.3 mg/L), three GACs, and two EBCTs. Between 7 and 11 PFAS breakthrough curves were available for each pilot column. RSSCT designs were investigated that assumed intraparticle diffusivity is independent of GAC particle size (i.e., constant diffusivity [CD]) or linearly dependent on GAC particle size (i.e., proportional diffusivity [PD]). CD‐RSSCTs effectively predicted the bed volumes of water that could be treated at the pilot‐scale to reach 50% breakthrough (BV50%) of individual PFAS. In contrast, PD‐RSSCTs overpredicted BV50% obtained at the pilot‐scale by a factor of ~2–3. The shape of PFAS breakthrough curves obtained with CD‐RSSCTs deviated from those obtained at the pilot‐scale, indicating that intraparticle diffusivity was dependent on GAC particle diameter (dp). Using the pore surface diffusion model (PSDM), intraparticle diffusivity was found to be proportional to (dp)0.25 when considering data up to about 70% PFAS breakthrough. This proportionality factor can be used to design RSSCTs or scale up existing CD‐RSSCT data using the PSDM. Using pilot‐scale data obtained with groundwater and wastewater‐impacted groundwater as well as with additional GACs, the developed RSSCT scale‐up approach was validated for PFAS breakthrough percentages up to 70%. The presented methodology permits the rapid prediction of GAC use rates for PFAS removal.

The Use of GAC (Granular Activated Carbon) and Zeolite as an Adsorbent to Reduce The Concentration of Phosphate in Laundry Wastewater

The growth of the laundry business increases every year along with population growth, however the laundry waste produced is generally thrown straight into the drain and flows into water bodies without prior treatment. The threshold limits for laundry wastewater quality standards for phosphate content, Chemical Oxygen Demand (COD) and Total Suspended Solid (TSS) are 10 mg/L respectively based on East Java Governor Regulation No. 72 of 2013. Disposing of laundry waste directly in large quantities into water bodies can have negative effects on the ecosystem in water bodies and water pollution problems. This research aims to determine the efficiency of using GAC and zeolite adsorbents in reducing phosphatelevels in laundry liquid waste. Based on the impact that can pollute water bodies, it is necessary to process laundry liquid waste. One of the processing methods used is the adsorption method, the adsorption process is carried out using Granular Activated Carbon (GAC) and zeolite with a batch system. This research uses liquid wastewater samples from laundry businesses. The variations used in this research are the adsorbent mass, and contact time. The results obtained from this research include SEM (Scanning Electron Microscopes) test results and the percentage reduction in phosphatelevels using GAC and zeolite adsorbents in batch systems. The research results show that the optimum adsorbent mass is 12 grams of adsorbent mixed with GAC and zeolite with a contact time of 150 minutes with a percentage reduction in phosphate levels of 57.14%. The phosphate values of laundry liquid waste after processing with adsorbent mass, adsorbent composition and optimum contact time are 6.5 mg/L.

Simultaneous regeneration of activated carbon and removal of adsorbed atrazine by ozonation process: From laboratory scale to pilot studies

A novel treatment technique by coupling granular activated carbon (GAC) adsorption and ozone regeneration was constructed for long-lasting water decontamination. The GAC adsorption showed high performance for atrazine (ATZ) removal (99.9 %), and the ozone regeneration ensured the recyclability of GAC for water purification. The regeneration process was evaluated via several paths to assist the efficient adsorption process. Employing ozone micro-nano bubbles (O3-MNBs) for regenerating GAC showed superior performance compared to traditional ozone. Meantime, inhibiting the formation of bromate (BrO3−). ATZ adsorption process suffered from the pore-filling, hydrogen bonding effect and π-π EDA interaction. The surface phenolic hydroxyl group, carboxyl group and pyridine nitrogen benefitted the triggering of ozone to generate reactive oxygen species, and regenerate the GAC surface. The superior performance of the adsorption and regeneration process was verified via a long-term running by a pilot study. It significantly improved the removal of organic micropollutants, UV254 and permanganate index. Additionally, the intermittent O3-MNBs regeneration process resulted in efficient decontamination within the pores structure of GAC, which also effectively preserved the pore structure from destruction. For actual application, the cost of water production can be saved around 0.63 kWh m−3. This work proposed new ideas and theoretical support for economic water production.

Pilot-scale removal of PFAS from chromium-plating wastewater by anion exchange resin and activated carbon: Adsorption difference between PFOS and 6:2 fluorotelomer sulfonate

Chromium-plating wastewater is an important source of per- and polyfluoroalkyl substances (PFAS) contamination. Currently, adsorption is considered to be one of the main technologies for the removal of PFAS from wastewater. However, no pilot-scale studies have been conducted to investigate its application in chromium-plating wastewater and the adsorption characteristics of 6:2 fluorotelomer sulfonate (6:2 FTS), the alternative to perfluorooctane sulfonate (PFOS). In this study, we evaluated the removal of PFAS from chromium-plating wastewater by granular activated carbon (GAC) and anion exchange resin (AER) at a pilot-scale. The breakthrough curves of PFOS and 6:2 FTS were similar in GAC columns, but significantly different in AER columns, with PFOS and 6:2 FTS reaching 10% breakthrough at about 45,000 BV and 4,000 BV, respectively. The replacement of 6:2 FTS by PFOS and other coexisting organic substances resulted in the concentrations of 6:2 FTS in the AER effluent reaching up to 3.8 times the influent concentrations. Density functional theory (DFT) calculations showed that the adsorption energy of PFOS on the quaternary amine group of AER was more negative than that of 6:2 FTS, and the weak affinity of AER for 6:2 FTS was closely related to the solvent effect. According to the cost analysis, if 6:2 FTS becomes the target PFAS, AER adsorption will no longer have a cost advantage over GAC adsorption. This study can provide technical support for the adsorptive removal of PFAS from electroplating wastewater and guide the development of efficient adsorbents for PFAS alternatives.

Utilization of magnetic GAC adsorbent for the removal of COD and BOD parameters in tofu wastewater

The tofu industry in Indonesia has mainly not processed its waste before it is discharged into the environment. This study seeks to ascertain the effectiveness of granular activated carbon magnetic adsorbents in removing pollutant characteristics from tofu wastewater. The effectiveness of the allowance resulting from the processing procedure will be assessed using variations in the mass of magnetic granular activated carbon and adsorption time. Granular Activated Carbon (GAC) and magnetic GAC production are activated using a modified green coprecipitation approach. Tofu wastewater samples used in this study contained COD of 5080 mg/L and BOD of 828 mg/L. The magnetic GAC variations with an adsorbent mass of 7.5 g/L and an absorption duration of 60 minutes, a COD value of 2930 mg/L, and an allowance ability of 42.32%, have the best ability to remove COD, according to the research done for the COD test. The allowed for the BOD parameters that produced the best results was 345 mg/L, and the 45-minute absorption time treatment with a GAC concentration of 10 g/L resulted in a removal efficiency of 58.38%.

Utilization of magnetic GAC adsorbent for the removal of TSS and turbidity parameters in tofu wastewater

The tofu industry in Indonesia is one of the most popular industries among Indonesians. Unfortunately, almost all tofu industries in Indonesia do not treat their wastewater correctly. Tofu liquid waste contains many pollutants as organic molecules and solids in suspension. This study aims to treat tofu liquid waste using magnetic GAC thus it is safe when when discharged into bodies of water. The adsorption process in tofu wastewater research is carried out using adsorbents. The adsorbent used is Granular Activated Carbon (GAC). The adsorbent activation process applies the wet activation method, and magnetic GAC is modified green coprecipitation method synthesis. Based on the completed research, it was found that the best allowance for turbidity test was the 15 minutes adsorption time treatment given a magnetic GAC concentration of 10 g/L with the removal efficiency of 73.92% and the best TSS concentration was adsorbtion with a magnetic GAC concentration of 7.5 g/L within 30 minutes adsorption time with a removal efficiency of 56.76%.

Regeneration of granular activated carbon adsorbent by peroxymonosulfate activation with MnO2/MnFe2O4

The regeneration of spent adsorbent is crucial in terms of environmental and economic aspects. In this study, MnO2/MnFe2O4 was synthesized by an impregnation-precipitation method and investigated as a peroxymonosulfate (PMS) catalyst for the regeneration of granular activated carbon (GAC) after adsorption of ofloxacin (OFL). MnO2/MnFe2O4 exhibited high catalytic activity for the regeneration of GAC with PMS, and the adsorbed OFL was effectively removed from GAC surface. Singlet oxygen was found to be the dominant reactive species in this process, while O2•− and SO4•− participated in the degradation of intermediates. At neural pH, the regeneration efficiency of the spent GAC after the adsorption of OFL, tetracycline hydrochloride, ciprofloxacin and methylene blue reached 100 %, 100 %, 87.2 % and 84.2 %, respectively. MnO2/MnFe2O4 and GAC exhibited good stability and reusability in this process, and the regeneration efficiency was still above 90 % in the fifth cycle. The results suggest the potential application of PMS activation with magnetic catalyst in the regeneration of GAC after adsorption of organic pollutants.

Multi-target assessment of advanced oxidation processes-based strategies for indirect potable reuse of tertiary wastewater: Fate of compounds of emerging concerns, microbial and ecotoxicological parameters

Two advanced oxidation processes (AOPs), namely ozone/H2O2 and UV/H2O2, were tested at pilot scale as zero-liquid-discharge alternative treatments for the removal of microbiological (bacteria and viruses), chemical (compounds of emerging concern (CECs)) and genotoxic responses from tertiary municipal wastewater for indirect potable reuse (IPR). The AOP treated effluents were further subjected to granular activated carbon (GAC) adsorption and UV disinfection, following the concept of multiple treatment barriers. As a reference, a consolidated advanced wastewater treatment train consisting of ultrafiltration, UV disinfection, and reverse osmosis (RO) was also employed.The results showed that, for the same electrical energy applied, the ozone/H2O2 treatment was more effective than the UV/H2O2 treatment in removing CECs. Specifically, the ozone/H2O2 treatment, intensified by high pressure and high mixing, achieved an average CECs removal efficiency higher than UV/H2O2 (66.8% with respect to 18.4%). The subsequent GAC adsorption step, applied downstream the AOPs, further improved the removal efficiency of the whole treatment trains, achieving rates of 98.5% and 96.8% for the ozone/H2O2 and UV/H2O2 treatments, respectively. In contrast, the ultrafiltration step of the reference treatment train only achieved a removal percentage of 22.5%, which increased to 99% when reverse osmosis was used as the final step.Microbiological investigations showed that all three wastewater treatment lines displayed good performance in the complete removal of regulated and optional parameters according to both national and the European Directive 2020/2184. Only P. aeruginosa resulted resistant to all treatments with a higher removal by UV/H2O2 when higher UV dose was applied. In addition, E. coli STEC/VTEC and enteric viruses, were found to be completely removed in all tested treatments and no genotoxic activity was detected even after a 1000-fold concentration.The obtained results suggest that the investigated treatments are suitable for groundwater recharge to be used as a potable water source being such a procedure an IPR. The intensified ozone/H2O2 or UV/H2O2 treatments can be conveniently incorporated into a multi-barrier zero-liquid-discharge scheme, thus avoiding the management issues associated with the retentate of the conventional scheme that uses reverse osmosis. By including the chemical cost associated with using 11–12 mg/L of H2O2 in the cost calculations, the overall operational cost (energy plus chemical) required to achieve 50% average CECs removal in tertiary effluent for an hypothetical full-scale plant of 250 m3/h (or 25,000 inhabitants) was 0.183 €/m3 and 0.425 €/m3 for ozone/H2O2 and UV/H2O2 treatment train, respectively.

Nano manganese dioxide coupling carbon source preloading granular activated carbon biofilter enhancing biofilm formation and pollutant removal

The formation of stable and mature biofilms affects the efficient and stable removal of ammonium by biological activated carbon (BAC). In this study, the new granular activated carbon (GAC) was preloaded with the carbon source (glucose and sucrose) and nano manganese dioxide (nMnO2) before using. Then tests were performed to determine whether substrate preloading promoted ammonium removal. The ammonium removal treated by nMnO2 coupled with sucrose-loaded BAC reached 49.1 ± 2.5%, which was 1.7 times higher than that by the nonloaded BAC 28.2 ± 1.9%). The biomass on the substrate-loaded BAC reached 5.83 × 106-1.22 × 107 cells/g DW GAC on Day 7, which was 4.6–9.5 times higher than the value of the nonloaded BAC (1.28 × 106 cells/g DW GAC). The amount of extracellular polymer (i.e., protein) on nMnO2 coupled to sucrose-loaded BAC was promoted significantly. Flavobacterium (0.7%–11%), Burkholderiaceae (13%–20%) and Aquabacterium (30%–67%) were the dominant functional bacteria on the substrate-loaded BAC, which were conducive to the nitrification or denitrification process. The results indicated that loading nMnO2 and/or a carbon source accelerated the formation of biofilms on BAC and ammonium removal. Additionally, the ammonium removal treated by nMnO2 coupled with sucrose-loaded BAC was contributed by microbial degradation (56.0 ± 2.5%), biofilm adsorption (38.7 ± 2.1%) and GAC adsorption (5.3 ± 0.3%), suggesting a major role of microbial degradation.

Removal of the waterborne parasite Cryptosporidium parvum from drinking water using granular activated carbon

Cryptosporidium is a genus of apicomplexan parasites that infect the gastrointestinal tract of a wide range of vertebrate hosts, including humans. These enteropathogens are commonly detected in surface waters and Cryptosporidium is responsible of numerous waterborne outbreaks in industrialised countries. Filters of granular activated carbon (GAC) are mainly used to eliminate emerging micropollutants or control unpleasant odour and taste in drinking water. Recently, GAC has been also employed for removal of microorganisms from different types of water. This work evaluates the capability of GAC in the elimination of the infective forms of Cryptosporidium parvum (oocysts) from drinking water. For this, well water was spiked with oocysts of C. parvum and passed through a chromatographic column filled with fresh GAC at different bed heights (5–50 cm) and a filtration rate of 100 mL/min, approximately. By immunofluorescence microscopy, the number of oocysts in the water samples was determined. The logarithmic reduction (LR) was calculated by comparing the number of oocysts quantified in the filtered samples and the corresponding influent samples. High efficiencies of GAC in removing C. parvum oocysts from water were obtained. Thus, with a bed height of 35 cm, removal efficiencies > 2 LR were achieved. The highest LR (3.47 ± 0.31) was observed when a GAC bed height of 50 cm was used. Taking into account the results obtained, C. parvum oocysts were eliminated remarkably and, therefore, GAC adsorption filters may be considered additional barriers against this waterborne enteropathogen in drinking water at the household level in developing countries.

Effect of granular activated carbon adsorption on mitigating microfiltration membrane fouling by algal organic matter

Abstract Algal blooms can seriously affect the operation of water treatment processes including low-pressure (micro- and ultrafiltration) and high-pressure (nanofiltration and reverse osmosis) membranes mainly due to the accumulation of algae-derived organic matter (AOM). This study investigated the effect of granular activated carbon (GAC) pretreatment on PVDF microfiltration performance for the removal of AOM. Dissolved organic matter (DOM) solution of commercial humic acid, extra- and intracellular organic matter from two species of algae, and Cyanobacteria were used for the investigation of the fouling potential of the membrane. A comparison study of different DOM removal and fouling behaviors of microfiltration (MF) after GAC adsorption as pretreatment was evaluated under variable GAC dosage and solution pH. Almost 15–20% improvement in flux and decline in irreversible fouling occurred due to the pretreatment using 1.0 g/L of GAC for an hour. The intracellular material caused higher membrane fouling than humic acid due to the hydrophilic nature of the AOM. Membrane fouling and decline in flux increased with increasing pH in the range of 5.0–8.0. The comparison results might help to provide insights into the real challenge of dealing with the treatment of algal-laden water.

Life cycle assessment and life cycle cost analysis of anion exchange and granular activated carbon systems for remediation of groundwater contaminated by per- and polyfluoroalkyl substances (PFASs).

Anion exchange resin (AER) and granular activated carbon (GAC) have emerged as prominent technologies for treatment of waters contaminated with per- and polyfluoroalkyl substances (PFASs). This study compares the life cycle environmental impacts and life cycle costs of remediating PFAS-contaminated groundwater with these competing technologies, using field pilot data to inform model inputs. Comparative analysis indicates that AER systems employing single-use "PFAS-selective" resins have lower environmental impacts and costs than systems using regenerable resins or GAC adsorbents, supporting its use in future remediation efforts. Use of GAC operated as a single-use adsorbent led to the highest emissions as well as the highest treatment costs, with thermally-reactivated GAC proving to be less impactful than regenerable AER treatment. Sensitivity analyses highlighted the dominance of media usage rate (MUR), which is highly dependent on the selected PFAS treatment goals, to determine environmental impacts and costs over a 30-year system life cycle. Selection of very stringent changeout criteria (e.g., detection of any PFASs in effluent) significantly reduces the advantages of single-use resins. For regenerable AER, environmental impacts were dominated by management of the PFAS-contaminated brine/co-solvent waste stream used to regenerate the adsorbent, as well as the cosolvent content of the regenerant mixture and the cosolvent recovery efficiency achieved via on-site distillation. High impacts estimated for GAC adsorption, the result of high MUR relative to ion exchange media, can be significantly reduced if spent adsorbents are reused after thermal reactivation, but impacts are still greater than those predicted for single-use ion exchange systems. Findings are expected to hold across a range of diverse sites, including drinking water systems treating more dilute sources of PFAS contamination, as PFAS breakthrough was not found to be highly sensitive to sourcewater PFAS concentrations.

Biodegradable dissolved organic carbon profiling reveals capacity of carbon‐based potable reuse treatment over a range of operating conditions

AbstractBiological treatment is gaining ground as a means to enhance removal of total organic carbon (TOC) as part of a multi‐barrier treatment train for water reuse. Here we applied biodegradable dissolved organic carbon (BDOC) analysis to evaluate the extent of removal of various TOC fractions through a pilot‐scale water reuse train employing flocculation/sedimentation, ozone, biologically active carbon (BAC), and granular activated carbon (GAC). BDOC analysis highlighted GAC and ozone treatments as critical to non‐biodegradable dissolved organic carbon removal and the need to optimize BAC performance to maximize GAC adsorption capacity. BDOC analysis was further applied to benchmark process performance to operational conditions, such as empty bed contact time (EBCT), occurrence of nitrification, and operational upsets. The lower EBCT proved to be less resilient to nonideal conditions. Overall, BDOC analysis proved an asset for understanding and improving operation of ozone/BAC/GAC treatments for water reuse.

Encapsulation of activated carbon into calcium alginate microspheres toward granular-activated carbon adsorbents for elemental mercury capture from natural gas.

Activated carbon (AC) is an effective adsorbent for removing environmental pollutants. However, the traditional powder form of AC shows difficulty in handling during application which widely limits its utilization on the industrial scale. Herein, to avoid such limitation, traditional AC powder was encapsulated into calcium alginate (CA) microspheres. Calcium alginate/activated carbon (CAA) composite microspheres were prepared via cross-linking of sodium alginate/activated carbon composite solutions in a calcium chloride solution. Furthermore, in order to boost adsorption affinity of CAA composite microspheres toward elemental mercury (Hg°), ammonium iodide (NH4I)-treated calcium alginate/activated carbon (NCA) composite microspheres were obtained by a simple impregnation method using NH4I treatment. The morphological, structural, and textural properties of the microspheres were characterized and their Hg° adsorptive capacity was tested at different temperatures. Interestingly, the maximum adsorption capacity of NCA adsorbent composite microspheres was determined as 36,056.5μg/g at a flow rate of 250mL/min, temperature of 25°C, and 500μg/Nm3 of Hg° initial concentration. The Gibbs free energy (ΔG°) for NCA adsorbent composite microspheres varied from - 8.59 to - 10.54kJ/mol indicating a spontaneous adsorption process with an exothermic nature. The experimental Hg° breakthrough curve correlated well with Yoon‒Nelson and Thomas models. The breakthrough time (tb) and equilibrium time (te) were found to be 7.5days and 23days, respectively. Collectively, the findings of this work indicate a good feasibility of using NCA composite microspheres as potential adsorbents for removing Hg° from natural gas.

Evaluation of the adsorption characteristics of dissolved organic matter using granular activated carbon (GAC) and the regeneration efficiency of denitrification, Electro-Fenton, and Sono-Fenton oxidation

This research explored the use of a granular activated carbon (GAC) column to treat dissolved organics in Combined Sewer Overflows (CSOs), a major river pollutant. The regeneration efficiency of spent GAC was assessed utilizing three distinct methods: biological denitrification, electro-Fenton oxidation, and Sono-Fenton oxidation. Among the six organics tested, sucrose and raw sewage demonstrated the most comparable adsorption characteristics. GAC adsorption factors are multifaceted, involving pore size, surface functional groups, and competing solution substances, rather than just organic matter hydrophobicity. The biological denitrification enabled the utilization of the adsorbed organic matter on spent GAC, consequently reducing the initial NO3-N concentration from 99 mg/L to 8 mg/L over a period of 48 hours. Electro-Fenton treatment revealed marginal performance differences between SUS-SUS and Ti/Pt-Ti/Pt; however, the latter proved superior in terms of electrode stability over prolonged use. A combined strategy employing ultrasound and Fenton treatment at a frequency of 40 kHz yielded marginally higher GAC regeneration efficiency (68.5%) as compared to that at 750 kHz (67.8%). Among all regeneration techniques applied in this investigation, the Sono-Fenton method showed the highest efficiency.

Ozone membrane contactor for tertiary treatment of urban wastewater: Chemical, microbial and toxicological assessment

A membrane ozone contactor, operated under continuous mode, was applied to promote the tertiary treatment of urban wastewater (UWW), targeting the removal of contaminants of emerging concern (CECs), bacterial disinfection, and toxicity reduction. This system relies on the homogeneous radial distribution of ozone (O3) in the reaction zone by “titration” through a microfiltration borosilicate tubular membrane, while the UWW swirls around the membrane and drags the O3 microbubbles generated in the membrane shell-side. The membrane is coated with titanium dioxide (TiO2-P25) and radiation can be externally supplied via four UV lamps. The ozonation tests were carried out with secondary-treated UWW collected in different seasons (winter and summer) and spiked with a mix of 19 CECs (10 μg L−1 each). For an O3 dose of 18 g m−3, the best performance was obtained by increasing the O3 concentration (maximum [O3]G,inlet of 200 g Nm−3) and decreasing the gas flow rate (minimum QG of 0.15 Ndm3 min−1), providing the highest ozone transfer yield (88 %) and, thus higher specific ozone dose (g O3 per g dissolved organic carbon). Under these conditions, removals >80 % or concentrations below the limit of quantification were obtained for up to 13 of the 19 CECs and reductions up to 5 log units for total heterotrophs and below the limit of detection for enterobacteria and enterococci. Tests including a UVC dose of 0.10 kJ L−1 enhanced disinfection ability but had no impact on CECs oxidation. After ozonation, the abundance of antibiotic resistant bacteria was reduced but not eliminated, and microbial regrowth after 3-day storage was observed. No toxic effect was detected on zebrafish embryos using a dilution factor of 4 for the ozonized UWW and when granular activated carbon adsorption was subsequently applied the dilution factor decreased to 2.

Recovery of green solvent contaminated with petroleum hydrocarbons by selective adsorption onto granular activated carbon

Ethyl lactate (EL) has served as a promising green solvent for oil extraction from drill cuttings wastes. Its high commercial price and huge volume consumption currently pose a constraint regarding operational costs and environmental burdens. Therefore, this work aims to propose the adsorption by granular activated carbon (GAC) as a facile method for recycling the spent EL contaminated with oil. The results from batch experiments revealed that the adsorption of oil in EL was favorable and endothermic, reaching the maximum oil adsorptive capacity of 1053 mg g−1 at 35 °C. The adsorption process was best described by the Freundlich isotherm and pseudo-first order kinetic models. Oil adsorption mechanisms were mainly controlled by film diffusion, hydrophobic interaction, and coalescence. The competitive adsorption of EL onto GAC through hydrogen bonding and covalent bonding was also observed. For column adsorption, all breakthrough curves were well explained by Clark and bed depth service time models. The maximum breakthrough removal efficiency of 99.3% was achieved from the flow rate of 1 mL min−1, initial oil of 500 mg L−1 and bed height of 12 cm. The spent GAC was regenerated by heating at 350 °C, provided with a regeneration efficiency of 95% after five adsorption-desorption cycles. The payback period of using EL extraction and recovery was estimated at 1.8 years, considering secure landfill as a baseline. These findings prove the industrial applicability of GAC adsorption for solvent recovery and promote EL as a more economically feasible solvent for greener management of oil-contaminated drill cuttings.

Electrochemically assisted transport of chlorinated hydrocarbons from aged to clean silt

In this work, the electrokinetic transport of pollutants from polluted to clean soil at two different temperatures is evaluated and validated with a simple phenomenological transport model. For this purpose, real samples highly contaminated with residues from the industrial production of lindane are used. The results show that the dragging of aged pollutant is almost nil (below 0.1% of the initial content), regardless of the experimental conditions tested. During the treatment, the resulting intensity decreases due to ion depletion in the silt. Electro-osmotic fluxes are quite low (0.7 cm d−1) and do not depend importantly on temperature. As well, the amounts of pollutants collected in electrolyte wells are negligible. However, there is an important volatilization (from 9 to 12% depending on operation temperature) of the chlorinated organic compounds (COCs) (mainly of lowly chlorinated organics and the gamma and delta isomers of hexachlorocyclohexane) but they are not recovered in the granular activated carbon adsorption but accumulated in the walls and pipes of the mockups. These results are confirmed by volatilization tests in closed bottles dragging the pollutants with an air flow. Additionally, the results accurately fit to a 1-D non-reactive model previously proposed to evaluate the transport of COCs from polluted to clean soil. Effective diffusion coefficients of COCs do not depend on the number of chlorine substitutions.

Pilot‐scale treatment cycle comprising membrane, thermal, and adsorption processes for spent metalworking fluids remediation

AbstractBACKGROUNDSpent metalworking fluids (SMWFs) represent a process waste characterized by low biodegradability, high toxicity, and very heterogeneous contamination typology connoted by the occurrence of numerous different pollutants. In this regard, the development of technically flexible and efficient treatment systems is fundamental to prevent sanitary and environmental risks deriving from SMWF disposal.RESULTSA treatment cycle including ultrafiltration (UF), evaporation, reverse osmosis (RO), and granular activated carbon (GAC) adsorption was tested at pilot scale for the remediation of three real SMWFs. A total of 44 parameters (physical, chemical, and ecotoxicological), identifying the SMWF characteristics and contamination, were analyzed after each treatment unit. The treatment cycle performance was investigated with and without the UF phase. In the complete cycle, UF was effective for the decrease of (average values) total suspended solids (96%), total hydrocarbons (>99%), animal fats and oils (>99%), and ecotoxicity (85%). In the same cycle, the evaporation significantly reduced the organic content (91% on average), and RO followed by GAC adsorption further provided effluents suitable for reuse in industrial applications. For the cycle without UF, parameters such as chemical oxygen demand, biochemical oxygen demand, and ecotoxicity showed values still significant (on average equal to 5550 mg L−1, 1933 mg L−1, and 95%, respectively) after evaporation. However, RO and GAC adsorption units allowed the achievement of effluents suitable for discharge in sewer systems.CONCLUSIONSAccording to the results, this work provides treatment strategies displaying high SMWF remediation efficiency and wide adaptability over various requirements for the achievement of specific effluent quality standards. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Ozonation and Granular Activated Carbon Adsorption for the Removal of Refractory Organic Matter and Decolorization During Wastewater Tertiary Treatment

This study investigated two different hybrid processes for the treatment of municipal secondary-treated biological effluents to meet the reuse of recycled water requirements for organic matter and color. The two hybrid treatment approaches were an oxidation-based treatment process (coagulation–sedimentation–deep-bed filtration [CSDF]–ozone oxidation) and an adsorption-based treatment process (CSDF-granular activated carbon [GAC] adsorption). The efficiencies of ozonation and GAC adsorption in removing chemical organic demand (COD), dissolved organic carbon (DOC), and color intensity were evaluated. The effect of CSDF as the pretreatment was also studied. Ozonation showed a much higher color removal efficiency (88%, 4.7 mg/L ozone dose) than GAC adsorption (23%). Organic matter with an apparent molecular weight of 2–3 kDa, being humus-like, might be the colored fraction in the secondary and CSDF effluents. Ozonation had a stronger ability to remove these substances than GAC adsorption, resulting in a visibly higher color removal efficiency. In addition, higher COD and DOC removal were achieved by ozonation when the average ozone dose was increased to 9.1 mg/L. Although both hybrid processes were reliable for reducing organic matter and color, the results show that ozonation is more suitable for simultaneously removing refractory organic matter and color.