Activated Carbon Pretreatment Research Articles

The effect of pretreatment on the adsorption efficiency of activated carbon

Activated carbon (AC) is a very diverse adsorbent material with high porosity, high surface area, and excellent performance in vapor phase adsorption. The pretreatment provides a guaranteed way for the efficient adsorption performance of AC, which can remove the impurities and improve the porosity of AC. In this study, the difference between acid pretreatment and alkali pretreatment of coconut shell carbon was systematically investigated. The effect of heating with stirring pretreatment and ultrasonic pretreatment after acid treatment were also researched. The Brunauer-Emmett-Teller (BET) specific surface area, the N2 saturation adsorption, and the porosity of AC by acid-ultrasonic pretreatment can reach 1094.30 m2g−1, 352.51 cm3 (STP) g−1, and 0.5453 cm3g−1, respectively, which are higher than that of acid-heating with stirring pretreatment and alkali-heating with stirring pretreatment. Combined with the Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS) analysis data, AC by acid-ultrasonic pretreatment has a better microstructure and clearer aperture. Among the three methods of preprocessing, acid-ultrasonic pretreatment yields the most favorable results. This work provides a possible way for AC pretreatment.

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.

Treatment and Valorization of Agro-Industrial Anaerobic Digestate Using Activated Carbon Followed by Spirulina platensis Cultivation

The increased production of biogas through the anaerobic digestion (AD) process has raised several concerns regarding the management of liquid digestate, which can present some environmental risks if not properly handled. Among the different techniques to treat AD digestate, microalgae and cyanobacteria cultivation has emerged as a sustainable approach to valorizing digestate while producing valuable biomass for production of biofuels and high value bioproducts. However, the intrinsic parameters of the liquid digestate can strongly limit the microalgae or cyanobacteria growth as well as limit the uptake of residual nutrients. In this study, the detoxification potential of activated carbon (AC) was evaluated on agro-industrial liquid digestate prior to Spirulina platensis cultivation. Different doses of AC, ranging from 5 to 100 g/L, were tested during adsorption experiments in order to determine the adsorption capacity as well as the removal efficiency of several compounds. Experimental results showed the high reactivity of AC, especially towards phosphate (PO4-P), total phenol (TP) and chemical oxygen demand (COD). At a dosage of 50 g/L, the AC pretreatment successfully achieved 54.7%, 84.7% and 50.0% COD, TP and PO4-P removal, corresponding to adsorption capacity of 94.7 mgDCO/g, 17.9 mgTP/g and 8.7 mgPO4-P/g, respectively. Even if the AC pretreatment did not show significant effects on Spirulina platensis growth during toxicity assays, the AC adsorption step strongly participated in the digestate detoxification by removing hardly biodegradable molecules such as phenolic compounds.

Integrating Ultrafiltration Membranes with Flocculation and Activated Carbon Pretreatment Processes for Membrane Fouling Mitigation and Metal Ion Removal from Wastewater.

The presence of metal ions in an aqueous medium is an ongoing challenge throughout the world. Processes employed for metal ion removal are developed continuously with the integration of these processes taking center stage. Herein, an integrated system consisting of flocculation, activated carbon (AC), and an ultrafiltration (UF) membrane was assessed for the removal of multiple metal ions contained in wastewater generated from a university chemistry research laboratory. The quality of the wastewater was established before and further determined after treatment with inductively coupled plasma optical emission spectrometry (ICP-OES) for metal content, total dissolved solids (TDS), turbidity, electrical conductivity (EC), and pH. Assessing the spent AC indicated minimal structural changes, indicating a potential for further reuse; for instance, the BET for both the pristine and spent AC exhibited type I isotherms with a mesoporous structure, indicating no major structural changes due to metal complexation. The relative performance of the integrated system indicated that the use of flocculation improved the water quality of metal-laden wastewater for safe disposal. The integrated treatment systems exhibited high removal efficiencies between 80 and 99.99% for all the metal ions except for Mn (<0.008 mg L-1) and Cr (<0.016 mg L-1) both at ca. 70%, indicative of the positive influence of the polyelectrolyte in the treatment process. The fabricated UiO-66-NH2@GO membranes (Z4 and Z5) exhibited high fouling resistance and reusability potential as well as relatively high pure water flux. Consequently, the integrated process employed for the treatment of laboratory metal-containing wastewater is promising as a generic approach to improving the quality of metal-containing wastewater to meet the standards of discharging limits in South Africa.

Mitigation of reverse osmosis membrane fouling by electrochemical-microfiltration- activated carbon pretreatment

In this study, a hybrid electrochemical-microfiltration-granular activated carbon adsorption (e-MF-GAC) pretreatment process was developed and demonstrated for controlling reverse osmosis (RO) fouling. Compared to ultrafiltration (UF), e-MF-GAC pretreatment resulted in 30% higher permeate flux. Results in this study show the complementarity among individual treatment processes of e-MF-GAC for removing inorganic/organic foulants and small organic molecules, leading to superior performance over conventional UF pretreatment. This hypothesis is validated by systematic feed water and foulant composition analysis as well as fluorescence excitation-emission matrix and X-ray diffraction spectroscopic characterization of the organic and inorganic foulants on the membrane surface, respectively. Organic foulants on the membrane were mostly protein-like compounds and their disposition onto the membrane surface was much lower after pretreatment using e-MF-GAC compared to UF. Similarly, after e-MF-GAC-RO pretreatment, organic content in the RO concentrate was lower than that after UF pretreatment. Results in this study provide the basis for further research at pilot scale to assess the economic viability of the proposed e-MF-GAC process as an alternative to conventional UF pretreatment for mitigating RO membrane fouling.

Unraveling competition versus adsorbability of dissolved organic matter against organic micropollutants onto activated carbon

It was widely acknowledged that dissolved organic matter (DOM) in natural water has ubiquitous competitiveness against organic micropollutants (OMPs) during adsorption onto activated carbon. However, some (model) low molecular weight organics have been reported to adsorb onto activated carbon, but were not competitive against co-adsorbates. The objective of this study is to identify which adsorbable DOM fractions in natural water contribute to the DOM competitiveness, and what is the impact of the OMP adsorbability and initial OMP concentration on this competitiveness. We, therefore, disassociated the adsorption of DOM fractions and OMPs (carbamazepine, caffeine and sulfamethoxazole) using a two-stage adsorption procedure, removing various adsorbable DOM fractions with powdered activated carbon pretreatment and then unraveling the competitiveness against OMPs of the remaining DOM. Our results demonstrated that DOM competition was not ubiquitous for all adsorbable fractions in natural water, and ∼ 25% of the adsorbable DOM was not competitive. The poorly adsorbable DOM was shown to be a non-competitive co-adsorbate, and its complexation even elevated the adsorption capacity of one of the OMPs (carbamazepine). The amount of DOM competitors increased for weaker adsorbable OMPs, and at higher initial OMP concentrations. The variability in DOM competition, differentiated by DOM adsorbability, has advanced the understanding of DOM competition, from ubiquitous competition to variable roles (varying competitiveness/complementary adsorption) of differently adsorbable DOM fractions during OMP adsorption.

Enhancement of pharmaceuticals treatment on activated sludge process by magnetic activated carbon pretreatment system

Enhancement of pharmaceuticals treatment on activated sludge process by magnetic activated carbon pretreatment system

Greywater reclamation: A comparison of the treatment performance of UiO-66-NH2@GO nanocomposites membrane filtration with and without activated carbon pretreatment

Composite polyethersulfone membranes incorporating UiO-66-NH2@GO were successfully prepared through phase inversion method. The membrane physico-chemical properties were established using a combination of techniques such as FTIR, SEM, TGA, AFM, and water contact angle whilst their performance was assessed using a benchtop membrane set-up. Important parameters such as pure water flux, fouling propensity as well as permeate were measured. Concomitant decrease in surface roughness, water contact angle, and porosity of the membranes improved with increasing UiO-66-NH2@GO filler content. The resulted modified membranes improved the antifouling properties. The quality of the treated greywater was upgraded to below minimum standards (SANS 1732: 2019) for reuse for pH, turbidity, electrical conductivity (EC), total dissolved solids (TDS). Integrating membranes with activated carbon pretreatment step further increased the antifouling profile of the membranes as seen through at least six greywater fouling-washing cycles. The current method, combination of activated carbon and ultrafiltration membranes, can be utilized to improve the greywater quality as an alternative cost-effective and simple treatment that meets the standards of non-potable water reuse.

Impact of biological activated carbon pre-treatment on the hydrophilic fraction of effluent organic matter for mitigating fouling in microfiltration

ABSTRACTThe hydrophilic (HPI) fraction of effluent organic matter, which has protein and carbohydrate contents, has a high propensity to foul low-pressure membranes. Biological activated carbon (BAC) filtration was examined as a pre-treatment for reducing the fouling of a microfiltration (MF) membrane (0.1 µm PVDF) by the HPI organic fraction extracted from a biologically treated secondary effluent (BTSE). Although the BAC removed less dissolved organic carbon, carbohydrate and protein from the HPI fraction than the granular activated carbon treatment which was used for comparison, it led to better improvement in permeate flux. This was shown to be due to the removal/breakdown of the HPI fraction resulting in less deposition of these organics on the membrane, many components of which are high molecular weight biopolymers (such as protein and carbohydrate molecules) through biodegradation and adsorption of those molecules on the biofilm and activated carbon. This study established the potential of BAC pre-treatment for reducing the HPI fouling of the membrane and thus improving the performance for the MF of BTSE for water reclamation.

Long-term operation of biological activated carbon pre-treatment for microfiltration of secondary effluent: Correlation between the organic foulants and fouling potential

The impact of long-term (>2 years) biological activated carbon (BAC) treatment for mitigating organic fouling in the microfiltration of biologically treated secondary effluent was investigated. Correlation between the organic constituents and hydraulic filtration resistance was investigated to identify the major components responsible for fouling. Over two years operation, the removal efficiency for dissolved organic carbon (DOC) by the BAC treatment was fairly consistent (30 ± 3%), although the reduction in UVA254 gradually decreased from 56 to 34%. BAC treatment effectively decreased the organic foulants in the effluent and so contributed to the mitigation of membrane fouling as shown by reduction in the unified membrane fouling index (UMFI). BAC consistently removed biopolymers whereas the removal of humic substances decreased from 52 to 25% after two years of BAC operation, and thus led to a gradual decrease in UMFI reduction efficiency from 78 to 43%. This was due to gradual reduction in adsorption capacity of the activated carbon as confirmed by analysis of its pore size distribution. Hence humics also played an important role in membrane fouling. However, there was a good correlation between protein and carbohydrate contents with hydraulically reversible and irreversible filtration resistance, compared with UVA254, turbidity and DOC. Although the mitigation of membrane fouling decreased over time, this study demonstrated that the long-term use of BAC pre-treatment of biologically treated secondary effluent prior to microfiltration has potential to reduce the need for frequent chemical cleaning and so increase membrane life span.

Powder Activated Carbon Pretreatment of a Microfiltration Membrane for the Treatment of Surface Water.

This study focused on the effect of powder activated carbon (PAC) adsorption on microfiltration (MF) membrane performance. The results showed that PAC pretreatment offered high organic matter removal rates for both dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UV254) during 10–200 mg/L PAC dosage. The removal efficiencies of organic matter by MF membrane filtration decreased with the increase of organic matter removal rate by PAC adsorption. PAC mainly removed organic matter of about 3 kDa molecular weight (MW). MF membrane maintained more than 5 kDa MW organic matter on the membrane after PAC adsorption. The results of membrane filtration indicated that PAC pretreatment slightly promoted membrane flux, regardless of PAC dosage. It seems that the organic matter fouling membrane was concentrated in more than 3 kDa MW. PAC removed markedly less than 3 kDa MW organic matter and had less effect on more than 3 kDa organic matter. Thus, PAC cannot reduce membrane fouling.

Enhanced l-lysine production from pretreated beet molasses by engineered Escherichia coli in fed-batch fermentation

Faster sugar consumption rate and low-cost nitrogen source are required for the chemical biosynthesis using molasses. Five pretreatment methods were applied to beet molasses prior to fermentation through engineered Escherichia coli, respectively, and corn steep liquid was used as an organic nitrogen source to replace expensive yeast extract. Furthermore, the effects of different feeding strategy in fed-batch fermentation on L-lysine production were investigated. The experimental results showed that combined tricalcium phosphate, sulfuric acid, and activated carbon pretreatment method (TPSA) pretreatment could improve the sugar consumption rate most greatly, and the initial total sugar concentration of 35 g/L from TPSA-pretreated beet molasses gave the best results with respect to L-lysine production, dry cell weight concentration, and L-lysine yield in batch fermentation. Moreover, a mixture of low-cost corn steep liquid and yeast extract containing equal amount of nitrogen could be used as the organic nitrogen source for effective L-lysine fermentation, and constant speed feeding strategy of TPSA-pretreated beet molasses promoted L-lysine production by engineered E. coli. The TPSA-pretreated beet molasses had a sugar consumption rate of 1.75 g/(L h), and a L-lysine yield of 27.81% was achieved, compared with the theoretical yield of 62% by glucose. It was clarified that the pretreatment significantly enhanced the conversion of sugars in beet molasses to L-lysine.

Effect of biological activated carbon pre-treatment to control organic fouling in the microfiltration of biologically treated secondary effluent

Biological activated carbon (BAC) filtration was investigated as a pre-treatment for reducing the organic fouling of a microfiltration membrane (0.1 μm polyvinylidene fluoride) in the treatment of a biologically treated secondary effluent (BTSE) from a municipal wastewater treatment plant. BAC treatment of the BTSE resulted in a marked improvement in permeate flux, which was attributed to the effective removal of organic foulants and particulates. Although the BAC removed significantly less dissolved organic carbon than the granular activated carbon (GAC) treatment which was used as a control for comparison, it led to a markedly greater flux. This was attributed to the effective removal of the very high molecular weight substances such as biopolymers by the BAC through biodegradation and adsorption of those molecules on the biofilm. Size exclusion chromatography showed the BAC treatment led to approximately 30% reduction in these substances, whereas the GAC did not greatly remove these molecules. The BAC treatment led to a greater reduction of loosely-attached and firmly-attached membrane surface foulant, and this was confirmed by attenuated total reflection-fourier transform infrared spectroscopy analysis. This study demonstrated the potential of BAC pre-treatment for reducing organic fouling and thus improving flux for the microfiltration of BTSE.

Modeling and Optimization for Production of Rice Husk Activated Carbon and Adsorption of Phenol

Modeling of adsorption process establishes mathematical relationship between the interacting process variables and process optimization is important in determining the values of factors for which the response is at maximum. In this paper, response surface methodology was employed for the modeling and optimization of adsorption of phenol onto rice husk activated carbon. Among the action variables considered are activated carbon pretreatment temperature, adsorbent dosage, and initial concentration of phenol, while the response variables are removal efficiency and adsorption capacity. Regression analysis was used to analyze the models developed. The outcome of this research showed that 99.79% and 99.81% of the variations in removal efficiency and adsorption capacity, respectively, are attributed to the three process variables considered, that is, pretreatment temperature, adsorbent dosage, and initial phenol concentration. Therefore, the models can be used to predict the interaction of the process variables. Optimization tests showed that the optimum operating conditions for the adsorption process occurred at initial solute concentration of 40.61 mg/L, pretreatment temperature of 441.46°C, adsorbent dosage 4 g, adsorption capacity of 0.9595 mg/g, and removal efficiency of 97.16%. These optimum operating conditions were experimentally validated.

Feasible pretreatment of textile wastewater for dark fermentative hydrogen production

In this study, the yield of hydrogen production was investigated under different feedstock pretreatment conditions. The feedstock for dark fermentative hydrogen production was textile wastewater which was obtained from the de-sizing process in a textile factory, located in northern Taiwan. The wastewater was pretreated with activated carbon, cation exchange resin or was not pretreated before being fed into the batch bottles. Biohydrogen production was carried out in a batch reactor with the sludge of mixed-culture using the feedstock from the pretreated wastewater. The sludge was obtained from the Taichung municipal wastewater treatment plant. The yield of hydrogen production using the two pretreatment methods or non – treatment were compared.Results showed that the textile wastewater could remove bio-toxic inhibitors by using activated carbon. The best hydrogen yield was 1.37 mol H2/mol reducing sugar with an initial pH 7.0, as substrate concentration was fixed at 20 g total sugar/L. Using textile wastewater as feedstock for biohydrogen production was successful, in removing bio-toxic inhibitors from wastewater with activated carbon pretreatment.

Effects of coconut granular activated carbon pretreatment on membrane filtration in a gravitational driven process to improve drinking water quality

This study evaluates the performance of a polymeric microfiltration membrane, as well as its combination with a coconut granular activated carbon (GAC) pretreatment, in a gravitational filtration module, to improve the quality of water destined to human consumption. The proposed membrane and adsorbent were thoroughly characterized using instrumental techniques, such as contact angle, Brunauer–Emmett–Teller) and Fourier transform infrared spectroscopy analyses. The applied processes (membrane and GAC + membrane) were evaluated regarding permeate flux, fouling percentage, pH and removal of Escherichia coli, colour, turbidity and free chlorine. The obtained results for filtrations with and without GAC pretreatment were similar in terms of water quality. GAC pretreatment ensured higher chlorine removals, as well as higher initial permeate fluxes. This system, applying GAC as a pretreatment and a gravitational driven membrane filtration, could be considered as an alternative point-of-use treatment for water destined for human consumption.

Effects of super-powdered activated carbon pretreatment on coagulation and trans-membrane pressure buildup during microfiltration

As a pretreatment for membrane microfiltration (MF), the use of powdered activated carbon (PAC) with a particle size much smaller than that of conventional PAC (super-powdered PAC, or S-PAC) has been proposed to enhance the removal of dissolved substances. In this paper, another advantage of S-PAC as a pretreatment for MF is described: the use of S-PAC attenuates trans-membrane pressure increases during the filtration operation. The floc particles that formed during coagulation preceded by S-PAC pretreatment were larger and more porous than the floc particles formed during coagulation preceded by PAC pretreatment and those formed during coagulation without pretreatment. This result was due to increased particle–particle collision frequency and better removal of natural organic matter, which inhibits coagulation by consuming coagulant, before the coagulation reaction. The caked fouling layer that built up on the membrane surface was thus more permeable with S-PAC than with normal PAC. Both physically reversible and irreversible membrane foulings were reduced, and more stable filtration was accomplished with S-PAC pretreatment.

Fundamental understanding of organic matter fouling of membranes

Among the different classifications of membrane fouling, organic fouling is perhaps the most poorly understood, with relationships to (organic) colloidal fouling and biofouling. Problematical foulants have been identified as polysaccharides and proteins but these components occur in both abiotic macromolecular and colloidal forms. In low-pressure membranes, there is some degree of hydraulic reversibility during backwashing but this option does not exist for high-pressure membranes; in both cases, the effectiveness of chemical cleaning is potentially constrained by the compatibility of membrane material with cleaning agent. Pretreatment by coagulation can reduce organic fouling while there is little consensus on the attributes of powdered activated carbon pretreatment. In general, the organic fouling behavior of membrane bioreactors (MBRs) is consistence with that of low-pressure membranes.

Aerobic biological treatment of 2,4-dinitrotoluene in munitions plant wastewater

Wastewater from the manufacture of propellants typically contains 2,4-dinitrotoluene (DNT), a known animal carcinogen. Previous studies have indicated that DNT is aerobically biodegradable. However, inconsistent removal of DNT during aerobic treatment has been observed at a munitions wastewater treatment plant, necessitating the use of activated carbon pretreatment. The objective of this study was to evaluate the effect of nutrient and cosubstrate amendments on the rate and extent of DNT removal. Addition of ethanol (100–500 mg/l) and phosphate (0.8–3.3 mg/l) significantly accelerated the rate of aerobic DNT (0.3–5.6 mg/l) biodegradation. Addition of phosphate alone also increased the rate of DNT degradation, but to a lesser degree. The presence of ethyl ether, another substrate commonly found in munitions plant wastewater, had comparatively little affect on the rate of DNT removal. Interruptions in the DNT manufacturing process can result in DNT being absent from the munitions plant wastewater for extended periods. The effect of such interruptions was evaluated in semicontinuously operated reactors, fed daily with phosphate-amended wastewater (containing no detectable background level of DNT), at a hydraulic residence time of 3 d. DNT was added at varying intervals (from once every 3 d to once every 15 d). DNT removal resumed without a lag even after it was absent from the feed for periods up to 15 d. During aerobic biodegradation of DNT, reduction to 4-amino-2-nitrotoluene and 2-amino-4-nitrotoluene was consistently observed, with reduction at the para position predominating. The highest level of aminonitrotoluene formation was 23% of the total DNT degraded. Aminonitrotoluene isomers were consumed within 1 d after the DNT disappeared in the semicontinuously operated reactors, confirming the potential for degradation of these metabolites. Although the aminonitrotoluene isomers are not currently regulated, their presence in treated munitions wastewater is a concern due to possible toxicity.

Ultrafiltration of lake water for potable water production

Ultrafiltration with coagulation or powdered activated carbon pretreatment is used to treat water from a public water supply. While UF without pretreatment is effective in removing turbidity, pretreatment prior to UF greatly enhances the removal of natural organic matter and trihalomethane precursors. Short-term flux loss can be minimized with backflushing, while long-term irreversible fouling seems to be affected most by the type of membrane polymer.