Adsorption Capacity Of Powdered Activated Carbon Research Articles

Removal of micropollutants from municipal wastewater using different types of activated carbons

The water reservoirs are getting polluted due to increasing amounts of micropollutants such as pharmaceuticals, organic polymers and suspended solids. Powdered activated carbon (PAC) has been proved to be a promising solution for the purification of water without having harmful impacts on the environment. Parameters such as PAC dosing, wastewater hardness, the effect of coagulant and flocculant were evaluated in a batch scale study. These parameters were further applied on a pilot plant scale for the performance evaluation of PAC based removal of micropollutants concerning the contact time and PAC dosing with main focus on recirculation of PAC sludge. The obtained optimum dose was 10–20 mg/L providing 84.40–91.30% removal efficiency of suspended solid micropollutants (MPs) and this efficiency increased to 88.90–93.00% along with coagulant which further raised by the addition of polymer and recirculation process at batch scale. On pilot plant scale, the concentration in contact reactor and PAC removal effectiveness of dissolved air flotation, lamella separator and sedimentation tank were compared. Constant optimisation resulted in a concentration ranging from 2.70 to 3.40 g/L at dosing of PAC 10 mg/L, coagulant 2.00 mg/L and polymer 0.50 mg/L. PAC doses of 10–20 mg/L with 15–30 min contact time proved best for above 70–80% elimination. The recirculation system has also proved an efficient technique because the PAC's adsorption capacity was practically completely used. Small PAC dosages yielded high micropollutants elimination.

Assessing the applicability of a new carob waste-derived powdered activated carbon to control pharmaceutical compounds in wastewater treatment

This paper assesses the applicability of a new carob waste-derived powdered activated carbon (PAC) obtained by steam activation for pharmaceutical compounds (PhCs) removal in urban wastewater treatment plants (WWTPs) with activated sludge (AS) secondary treatment. The new carob-derived PAC presents chemical and textural properties similar to a high-performing commercial PAC produced from vegetable source by physical activation. The adsorption isotherms of three target PhCs, carbamazepine, diclofenac and sulfamethoxazole, spiked (at around 100 μg/L) in mixed liquor (ML) and in clarified-ML from the AS-bioreactor of a WWTP show: (i) minor reduction of PAC capacity with real MLs compared to clarified MLs; (ii) the higher the PhC hydrophobicity, the higher the PAC adsorption capacity in both water matrices; (iii) hydrophobic interactions probably overweight electrostatic interactions between the PhCs and the slightly positively charged PAC in these real water matrices with background organics and inorganics. The PhC adsorption results with ML and clarified-ML are used to calibrate the IAST-based tracer model (TRM) and predict the new PAC performance when added to AS-bioreactor vs. in post-secondary treatment, at the PhC naturally-occurring trace concentrations. The modelling projections show (i) one needs higher PAC doses than those reported in the literature, particularly in post-treatment, and (ii) the benefits of PAC dosing to the bioreactor, with only a slightly higher PAC dose being needed when compared to its post-secondary dosing and minimising the capital investment.

Removal of Organic Pollutants from Effluent of Anaerobic Digester Using Hydrochars Produced from Faecal Simulant and Sewage Sludge

Hydrochars produced from hydrothermal carbonisation of faecal simulant (FS) at 180 °C for 30 min and sewage sludge treated via CAMBI process at 165 °C for 30 min were used for adsorption of organic pollutants in effluent from an anaerobic digester (AD). The adsorption potential of the hydrochars investigated was compared with that of a commercial powdered activated carbon (PAC). It was found that the CAMBI and FS hydrochars were effective only after chemical activation. KOH activation increased chemical oxygen demand (COD) removal from 33.0 to 59.6% and 75.2% for FS and CAMBI, respectively. Extra activation with HCl improved the adsorption efficiency of FS, increasing COD removal to 79.3%, but not for the CAMBI hydrochar even though its surface area was increased. Acidic pH aided organics removal for both hydrochars. PAC adsorption capacity was the highest (> 90%), and this was not affected by pH. All the adsorbents could successfully remove the organics in a very short time as 30 min. The optimum dosage of the hydrochars to reach a high uptake of organics was 30.0 g/L. The adsorption reaction followed a pseudo-second-order kinetic model for all the hydrochars. The adsorption onto the hydrochars correlated well with Temkin isotherm model and followed a type II and IV isotherm type, except PAC which was described by the Langmuir isotherm with a high adsorption capacity of 400.0 mg/g. The study demonstrated that hydrochars of FS and CAMBI activated with KOH are efficient and sustainable adsorbents for the removal of organics from AD effluent.

Regeneration of Rhodamine B saturated activated carbon by an electro-peroxone process

Due to the lack of feasible regeneration methods, spent powdered activated carbon (PAC) is conventionally disposed of by incineration or landfill after its adsorption capacity is exhausted in adsorption applications. In this study, an electro-peroxone (EP) process (a combined process of conventional ozonation and in situ cathodic hydrogen peroxide (H2O2) production) was proposed to regenerate PAC saturated with Rhodamine B (RhB) dye. Results show that the adsorption of RhB onto PAC involved primarily irreversible chemisorption. Therefore, the RhB-saturated PAC could not be regenerated upon dilution by water washing. In contrast, by oxidatively converting irreversibly sorbed RhB to more desorbable oxidation by-products (e.g., carboxylic acids), both ozonation and the EP regenerations could restore >90% of the adsorption capacity of the PAC for RhB reloading. However, ozonation regeneration could not effectively mineralize the desorbed pollutants due to the selective oxidation characteristics of ozone (O3). In contrast, due to the substantial generation of hydroxyl radicals (OH) from the reaction of bubbled O3 with electro-produced H2O2, the EP regeneration was capable of completely mineralizing the desorbed pollutants. During the EP regeneration, PAC was oxidized to some extents, thus gradually losing its adsorption capacity. By optimizing the applied current, ozone dose, and regeneration time, ∼76% of the adsorption capacity of the virgin PAC could still be retained after five cycles of RhB adsorption and the EP regeneration. The results of this study indicate that the EP process may provide an environmentally-friendly and sustainable way to regenerate spent PAC for reuse.

Pilot-scale study of powdered activated carbon recirculation for micropollutant removal.

Adsorption onto powdered activated carbon (PAC) is a promising technique for the removal of organic micropollutants (OMPs) from treated wastewater. To enhance the adsorption efficiency, PAC is recycled back into the adsorption stage. This technique was examined in pilot scale in comparison to a reference without recirculation. Coagulation with Fe(3+) was carried out simultaneously to adsorption. Extensive OMP measurements showed that recirculation significantly increased OMP eliminations. Thus, significant PAC savings were feasible. The PAC concentration in the contact reactor proved to be an important operating parameter that can be surrogated by the easily measurable total suspended solids (TSS) concentration. OMP eliminations increased with increasing TSS concentrations. At 20 mg PAC L(-1) and 2.8 g TSS L(-1) in the contact reactor, well-adsorbable carbamazepine was eliminated by 97%, moderately adsorbable diclofenac was eliminated by 92% and poorly-adsorbable acesulfame was eliminated by 54% in comparison to 49%, 35% and 18%, respectively, without recirculation. The recirculation system represents an efficient technique, as the PAC's adsorption capacity is practically completely used. Small PAC dosages yield high OMP eliminations. Poorly-adsorbable gabapentin was eliminated to an unexpectedly high degree. A laboratory-scale biomass inhibition study showed that aerobic biodegradation removed gabapentin in addition to adsorption.

Impact of salinity and dispersed oil on adsorption of dissolved aromatic hydrocarbons by activated carbon and organoclay

Adsorption capacity of phenol and naphthalene by powdered activated carbon (PAC), a commercial organoclay (OC) and a lab synthesized organoclay (BTMA) was studied using batch adsorption experiments under variable feed water quality conditions including single- and multi- solute conditions, fresh water, saline water and oily-and-saline water. Increasing salinity levels was found to reduce adsorption capacity of OC, likely due to destabilization, aggregation and subsequent removal of organoclay from the water column, but did not negatively impact adsorption capacity of PAC or BTMA. Increased dispersed oil concentrations were found to reduce the surface area of all adsorbents. This decreased the adsorption capacity of PAC for both phenol and naphthalene, and reduced BTMA adsorption of phenol, but did not negatively affect naphthalene removals by either organoclay. The presence of naphthalene as a co-solute significantly reduced phenol adsorption by PAC, but had no impact on organoclay adsorption. These results indicated that adsorption by PAC occurred via a surface adsorption mechanism, while organoclay adsorption occurred by hydrophobic or pi electron interactions. In general, PAC was more sensitive to changes in water quality than either of the organoclays evaluated in this study. However, PAC exhibited a higher adsorption capacity for phenol and naphthalene compared to both organoclays even in adverse water quality conditions.

The influence of chlorinated aromatics’ structure on their adsorption characteristics on activated carbon to tackle chemical spills in drinking water source

This study focused on evaluating the efficiency of powdered activated carbon (PAC) adsorption process and tackling chlorobenzenes and chlorophenols spill in drinking water source. The adsorption kinetics and PAC's capacities for five chlorobenzenes and three chlorophenols at drinking water contamination levels were studied in order to determine the influence of different functional groups on the adsorption behavior. The results showed that PAC adsorption could be used as an effective emergency drinking water treatment process to remove these com- pounds. The adsorption kinetics took 30 min to achieve nearly equilibrium and could be described by both pseudo first-order and pseudo second-order models. A mathematic relationship was developed between the pseudo first-order adsorption rate constant, k1, and the solutes' properties including lgKow, polarizability and molecular weight. The Freundlich isotherm equation could well describe the adsorption equilibrium behaviors of chlorinated aromatics with r 2 from 0.920 to 0.999. The H-bond donor/acceptor group, hydrophobicity, solubility and molecular volume were identified as important solute properties that affect the PAC adsorption capacity. These results could assist water professionals in removing chlorinated aromatics during emergency drinking water treatment.

Batch equilibrium analysis for the removal of hexavalent chromium: analysis of uncertainties using numerical modelling

Abstract Adsorbents like water hyacinth leaf, powdered activated carbon (PAC), PAC in combination with polymer beads (added to enhance the porosity) and a combination of PAC with water hyacinth leaves were used to remove hexavalent chromium from wastewater. Equilibrium was achieved after approximately 18 h. The maximum equilibrium sorption capacity (q max), determined from Langmuir isotherm, are: ADRB1: 9.638 mg/g; ADRB2: 31.46 mg/g; ADRB3: 55.926 mg/g; ADRB4: 33.575 mg/g for 1l wastewater solutions. The adsorption capacity of PAC (ADRB3) has been found more than the composite ADRB4 with a combination of WH (2 g) and PAC (1 g). However, ADRB4 could be used for applications where large quantity of wastewater (e.g. leather complexes) containing hexavalent chromium is disposed into a huge water body where plenty of water hyacinths are grown naturally. Simultaneously three isotherms namely Tempkin, Freundlich and Langmuir were parameterized. The parameters were estimated using the Levenburg and Marquardt opti...

Removal of natural organic matter from potential drinking water sources by combined coagulation and adsorption using carbon nanomaterials

In recent years, carbon nanomaterials have become promising adsorbents for water treatment. In this study, combined coagulation–adsorption treatment using single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) was employed for the removal of natural organic matter (NOM) from various water sources; powdered activated carbon (PAC) was used for comparison. Synthetic seawater and brackish water were produced, with humic acid as the source of NOM. Natural surface water was obtained from Broad River in Columbia, South Carolina. Synthetic landfill leachates were created to reflect the typical characteristics of leachate produced in young and old landfills. Glucose and humic acid were used as the NOM sources for the young and old leachates, respectively. Adsorption isotherm experiments were conducted to determine the adsorption capacity of each carbon nanomaterial, and jar testing was conducted to simulate the combined coagulation–adsorption treatment processes. The adsorption capacity of SWCNTs was greater than that of MWCNTs for the source waters. The adsorption capacity of PAC (log Kf=2.28–2.82) was generally higher than that of SWCNTs (log Kf=1.98–2.27) and MWCNTs (log Kf=1.08–1.16) in the case of source waters with low NOM content (i.e., seawater, brackish water), but was lower than those of SWCNTs and MWCNTs in the case of natural water and synthetic landfill leachates. NOM removal using the combined coagulation–adsorption process was more effective than the sole use of the adsorbent, regardless of the type of adsorbent. However, combined coagulation–adsorption treatment using SWCNTs, except in the case of the young leachate, resulted in the highest NOM removal (>90%) among the various combinations. PAC often outperformed MWCNTs in these combined treatment processes, except in the case of the young leachate. While MWCNTs have often been viewed as less-effective adsorbents, they were the most effective nanomaterial for removing NOM from the young leachate in the combined process (35.1% with aluminum sulfate; 17.4% with ferric chloride). When employing the combined coagulation–adsorption process, increases in adsorbent doses had little effect on the overall NOM adsorption. The results of this study show that combined coagulation–adsorption treatment using carbon nanomaterials can be effective in removing NOM from various water sources.

Simulation of Countercurrent Operation of Two-Stage Hybrid PAC-Submerged Membrane System for Trace Organics Removal

A countercurrent two-stage hybrid powdered activated carbon-submerged membrane (PAC-SM) system for atrazine removal was simulated numerically in the present work. The simulation of the system performance at different operating conditions confirms that the adsorption capacity of the powdered activated carbon (PAC) can be further utilized and a stable product water quality can be maintained in the countercurrent two-stage mode as compared with the concurrent single-stage operations. For instance, the utilization of the PAC adsorption capacity was enhanced by 28% in the countercurrent two-stage operation at a flux of 60 L/m2h, and 21% of enhancement was obtained at a flux of 100 L/m2h by more frequent PAC replacement. Therefore, the adsorption capacity utilization is also dependent on the membrane filtration flux. Moreover, if the final effluent concentration was controlled at a higher level (e.g., C2*=0.1 instead of C2*=0.05), a further 5% of the PAC adsorption capacity can be utilized. In addition, reducing the replacement rate (RR) will make the operation similar to a system with continuous PAC dosing (pseudo-steady-state) by presenting nearly constant product water quality. This study sheds some light on the performance of a countercurrent multistage hybrid PAC-SM system for its further applications and system optimization.

Adsorption of Perfluorinated Compounds onto Activated Carbon and Activated Sludge

The adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) onto powdered activated carbon (PAC) was investigated in the presence and absence of effluent organic matter (EfOM) at an environmentally relevant concentration range (0.1–500 μg/L). Adsorption of PFOS and PFOA to PAC fitted the Freundlich model well (r2>0.98), and adsorption capacity of PFOS (KF=17.48) and PFOA (KF=10.03) in the absence of EfOM was more than one order of magnitude higher than that in the presence of EfOM (KF=0.66 for PFOS, KF=0.20 for PFOA), indicating that EfOM greatly reduces the adsorption capacity of PAC. Moreover, EfOM was characterized by ultrafiltration, and fractions of nominal molecular weights were obtained to investigate their effect on the PFOS and PFOA adsorption. The fraction of 30 kDa, indicating that the similar molecular size of target compounds was the major contributor to adsorption competition. Additionally, biosorption of P...

Adsorption of Reactive Black 5 from an aqueous solution: equilibrium and kinetic studies

Removal of a reactive dye, Reactive Black 5, from an aqueous solution was studied by adsorption on powdered activated carbon (PAC) and Afsin-Elbistan fly ash (Turkey). The adsorption of the dye on PAC and fly ash was investigated during a series of batch adsorption experiments carried out to determine the effect of initial dye concentration and contact time. The amounts adsorbed at equilibrium were measured. The Langmuir and Freundlich isotherm models were tested for their applicability. The equilibrium data satisfied both Langmuir and Freundlich models. The adsorption capacity of PAC and fly ash were found to be 58.823 mg and 7.936 mg dye per gram of adsorbent, respectively. The experimental data were analysed using the pseudo-first-order and pseudo-second-order adsorption kinetic models. According to these models, the rate constants were evaluated for initial dye concentrations. The experimental data fit the second-order kinetic model.

Evaluation of the performance of adsorption and coagulation processes for the maximum removal of reactive dyes

Physicochemical processes of adsorption and coagulation were systematically evaluated for the removal of reactive dyes (Orange 16 and Black 5) in a laboratory scale experimental setup. The effectiveness of combined processes of adsorption and coagulation for complete removal of dyes was also investigated. The right sequence of operation was identified for the combined treatment system. A coconut-based powdered activated carbon (PAC) was used as an adsorbent and alum chloride was chosen as a coagulant. The results indicated that adsorption capacity of Orange 16 was much higher than that of Black 5. Also, adsorption capacity on PAC was highly dependent on the pH of solution. The dye removal efficiencies for 100 mg l −1 of Black 5 and Orange 16 by coagulation were almost 99% and 80% under the determined optimal conditions for Black 5 (250 mg l −1 coagulant dose and pH 6) and for Orange 16 (350 mg l −1 coagulant dose and pH 6). Coagulation followed by adsorption was found to be more efficient than having adsorption prior to coagulation. There was a significant increase in adsorption capacity of PAC for the combined process where coagulation was carried out prior to adsorption. The combined coagulation–adsorption process has the capability of complete dye removal and thus total decolourization, reduction in coagulant and adsorption amounts and thereby produce less amount of sludge.

Adsorption capacity of powdered activated carbon for 3,5-dichlorophenol in activated sludge

The objectives of this study were to evaluate the performance of powdered activated carbon treatment (PACT) process based on the adsorption capacity of powdered activated carbon (PAC) in activated sludge and the effect of dissolved organic substances in activated sludge on the adsorption capacity of PAC. The DCP adsorption capacity of three PACs originated from different raw materials (coal, soft coal and sawdust) in activated sludge were 29%, 34% and 17% of that of new PAC, respectively. The performance of PACT process for shock loading of 3,5-dichlorophenol (3,5-DCP) was different among PACs in spite of the same adsorption capacity in new PAC. The performance of PACT process for removal of DCP is dependent not on the adsorption capacity of new PAC but on the adsorption capacity of PAC in the aeration tank. Dissolved organic matter (DOM) with molecular weight smaller than 50 kDa did not affect the adsorption capacity of PAC for 3,5-DCP in the activated sludge reactor. DOM with molecular weight larger than 50 kDa and biofilm developed on the surface of PAC seemed to be responsible for the decreased adsorption capacity of PAC for the DCP.

Development of advanced ceramic membrane filtration system combined with ozonation and powdered activated carbon treatment

Combining the Kubota Tank-Submerged type Ceramic Membrane filtration (TSCM) system with ozonation and powdered activated carbon (PAC) treatment, a new water treatment system, the advanced TSCM system, has been developed. It is a compact, maintenance-free and high performance system for water treatment plants in the small and medium size cities. In this paper, experimental results using 5.5m3/day demonstration plants are shown, and treatment performance is discussed mainly focussing on removal of disinfection by-products. Turbidity, color, total iron, total manganese and ammonia nitrogen were removed to below their detection limits. Accumulation of suspended solids including PAC at a maximum concentration of 8000 mg/L in the membrane tank increases biological degradation activity in the TSCM system. Furthermore, it was confirmed that the advanced TSCM system was able to effectively eliminate disinfection by-products and other organic contaminants in raw water. 75% of T-THMFP removal rate was obtained at only 10 mg-PAC/L dosage without the effect of ozone dosage, while the PAC treatment at 50 mg-PAC/L dosage prior to coagulation results in T-THMFP removals ranging from 40 to 60% (The Adoption Guideline of Advanced Water Treatment Facility, 1988). Therefore, it is concluded that the advanced TSCM system saves on the amount of PAC and is more cost-effective than the other conventional water treatment systems due to efficient utilization of the adsorption capacity of PAC.

Mathematical modeling of PAC adsorption processes

Easy‐to‐use models for PAC adsorption processes are presented.Recently, great strides have been made in modeling the adsorption of organic compounds onto powdered activated carbon (PAC), specifically with the conversion of the partial differential equations of the homogeneous surface diffusion model to algebraic nonlinear equations. The solutions of these equations are easy to obtain using nonlinear equation‐solving techniques (such as Newton's method) and are as accurate as the partial differential equation solutions obtained using labor‐intensive numerical techniques. A new method using these algebraic equations has been developed to determine the value of the surface diffusion coefficient Ds from adsorption batch kinetic tests. A nondimensional parameter λ = (t Ds/R2) can be used to evaluate the performance of PAC in a continuous‐flow process. A λ value > 0.1 implies that the adsorption process is highly efficient, in that more than 75 percent of the PAC adsorption capacity is being utilized. On the other hand, a λ value < 0.01 implies that the adsorption process is highly inefficient, in that less than 30 percent of the PAC adsorption capacity is being utilized.

活性炭共存微生物包括固定化法によるジベンゾフランの処理特性

The development of biological advanced treatment of dioxins in the pulp waste water using immobilized microbes was studied. Microorganisms were immobilized by photo-crosslinked resin with powdered activated carbon (PAC). The effect of adsorption capacity of PAC, adaptation of microorganisms to pulp waste water, and biodegradability of dibenzofuran (DBF), carbon based skeletal structure of dioxins were examined.The results obtained from this study were as follows.1) Immobilized microorganisms with PAC removed DBF more effectively due to the adsorption and concentration effect of PAC.2) Immobilized microorganisms such as Pseudomonas aeruginosa effectively removed organic matter and degraded DBF in the waste water.3) DBF removal rate and ATP content of immobilized microorganisms were more rapid and higher than those of suspended microorganisms.4) The adsorption capacity of PAC was reduced due to gel inhibition effect, however, immobilized PAC has worked effectively to DBF treatment.

Removal of 2,4,6-trichlorophenol and natural organic matter from water supplies using PAC in floc-blanket reactors

The objective of this study was to evaluate the addition of powdered activated carbon (PAC) to upflow floc-blanket reactors for the adsorption of natural and synthetic organic chemicals. A 15.5-1. bench-scale floc-blanket reactor was operated with PAC addition for the adsorption of 2,4,6-trichlorophenol (TCP) and natural organic matter from one groundwater and two surface waters under laboratory and field conditions, respectively. Influent TCP concentrations ranged from 21 to 415 μg/l. The PAC doses ranged from 2 to 12 mg/l. While the hydraulic residence time in the floc-blanket reactor varied from 15 to 30 min, the carbon residence time ranged from 9 to 34 h. This is due to the high solids concentration in the floc blanket, which ranged from 1200 to 8700 mg/l. Comparison between the extent of TCP adsorption through the floc-blanket reactor and the equilibrium adsorption isotherms of TCP on PAC showed that the maximum adsorption capacity of PAC for TCP was utilized in the reactor. However, this study showed that the maximum adsorptive capacity of the carbon in a continuous process is dependent on the influent adsorbate concentration. This was in agreement with isotherm studies conducted with varying initial TCP concentration. The maximum PAC adsorption capacity for natural organic matter was also achieved in the floc-blanket reactor.