Preparation of H-oleoyl-carboxymethyl-chitosan and the function as a coagulation agent for residual oil in aqueous system

In this study, H-form oleoyl-carboxymethyl-chitosan (H-O-CMCS) was prepared as a coagulation agent to clean up the residual oil from the waste-water of oil extraction (WWOE). The Fourier transform infrared (FTIR) spectra confirmed the formation of an amide linkage between amino groups of carboxymethyl chitosan (CMCS) and carboxyl groups of oleic acid. The adsorption capacities of four absorbents (H-O-CMCS, chitosan, activated carbon and polyaluminium chloride (PAC)) for the residual oil were investigated. Compared with chitosan, activated carbon and PAC, H-O-CMCS was more effective in removing the residual oil from WWOE, which could successfully wash up almost 99% of residual oil from WWOE at the dosage of 0.2 g/L, the mixing time of 3 min, 500 rpm, and a broader range of pH (the system temperature ≤45°C). In similar conditions, comparatively, chitosan, activated carbon and PAC could wash 90%, 82% and 92% of residual oil from WWOE, respectively.     

Preparation of a pitch-based activated carbon with a high specific surface area

Pitch based activated carbons (PAC) with a high specific surface area were produced by a direct chemical activation route in which oxidative stabilized pitch derived from ethylene tar oil was reacted with potassium hydroxide under various activation conditions. It was found that PACs with a surface area of around 2600–3600 m² g^-1 could be obtained under suitable activation conditions. N₂ adsorption (at 77 K) and X-ray photoelectron spectroscopy experiments showed that the PAC has a uniformly developed micropore structure and a narrow pore size distribution (radius 0.8–1.6 nm). Abundant oxygen-containing functional groups (such as C–OH, C–O–C, C=O, COOR etc.) were found to exist on its surface. Compared with a commercially available activated carbon (AC) and also a pitch based activated carbon fibre, PAC has a quicker adsorption–desorption velocity and a larger adsorptive capacity to benzene due to its higher surface area. Clear surface differences between PAC and AC were observed by transmission electron microscopy. This revised version was published online in November 2006 with corrections to the Cover Date.     

Removal of organic pollutants from produced water by batch adsorption treatment

This paper studied the adsorption of chemical oxygen demand (COD), oil and turbidity of the produced water (PW) which accompanies the production and reconnaissance of oil after treating utilizing powdered activated carbon (PAC), clinoptilolite natural zeolite (CNZ) and synthetic zeolite type X (XSZ). Moreover, the paper deals with the comparison of pollutant removal over different adsorbents. Adsorption was executed in a batch adsorption system. The effects of adsorbent dosage, time, pH, oil concentration and temperature were studied in order to find the best operating conditions. The adsorption isotherm models of Langmuir, Freundlich and Temkin were investigated. Using pseudo-first-order and pseudo-second-order kinetic models, the kinetics of oil sorption and the shift in COD content on PAC and CNZ were investigated. At a PAC adsorbent dose of 0.25 g/100 mL, maximum oil removal efficiencies (99.57, 95.87 and 99.84 percent), COD and total petroleum hydrocarbon (TPH) were identified. Moreover, when zeolite X was used at a concentration of 0.25 g/100 mL, the highest turbidity removal efficiency (99.97%) was achieved. It is not dissimilar to what you would get with PAC (99.65 percent). In comparison with zeolites, the findings showed that adsorption over PAC is the most powerful method for removing organic contaminants from PW. In addition, recycling of the consumed adsorbents was carried out in this study to see whether the adsorbents could be reused. Chemical and thermal treatment will effectively regenerate and reuse powdered activated carbon and zeolites that have been eaten.

Graphic abstract

     

Remediation of hexachlorobenzene contaminated soils by rhamnolipid enhanced soil washing coupled with activated carbon selective adsorption

The present study investigates the selective adsorption of hexachlorobenzene (HCB) from rhamnolipid solution by a powdered activated carbon (PAC). A combined soil washing-PAC adsorption technique is further evaluated on the removal of HCB from two soils, a spiked kaolin and a contaminated real soil. PAC at a dosage of 10 g L(-1) could achieve a HCB removal of 80-99% with initial HCB and rhamnolipid concentrations of 1 mg L(-1) and 3.3-25 g L(-1), respectively. The corresponding adsorptive loss of rhamnolipid was 8-19%. Successive soil washing-PAC adsorption tests (new soil sample was subjected to washing for each cycle) showed encouraging leaching and adsorption performances for HCB. When 25 g L(-1) rhamnolipid solution was applied, HCB leaching from soils was 55-71% for three cycles of washing, and HCB removal by PAC was nearly 90%. An overall 86% and 88% removal of HCB were obtained for kaolin and real soil, respectively, by using the combined process to wash one soil sample for twice. Our investigation suggests that coupling AC adsorption with biosurfactant-enhanced soil washing is a promising alternative to remove hydrophobic organic compounds from soils.     

The removal of algal biomass and extracellular products from water

Abstract

The removal of algal biomass and algal extracellular products (ECPs) from eutrophic water is studied using various physical chemical methods including coagulation/precipitation, powdered activated carbon (PAC) adsorption and combination of coagulation/ precipitation and activated carbon adsorption. The removal efficiencies of algae and TOC are 96% and 81%, respectively, by coagulation/ precipitation method. Moreover, dissolved organic carbon (DOC) is divided into four groups based on molecular weight distribution. It is found that coagulation/ precipitation process has good DOC removal efficiency for high molecular weight groups whereas PAC adsorption is particularly effective of the removal of DOC of low molecular weight. It is also discovered that the removal efficiency is synergistic by coagulation/ precipitation followed by PAC adsorption. The formations of THMFP/ DOC and AOXFP/DOC are higher with high molecular weight groups than those with low molecular weight groups.     

Performance enhancement with powdered activated carbon (PAC) addition in a membrane bioreactor (MBR) treating distillery effluent

This work investigated the effect of powdered activated carbon (PAC) addition on the operation of a membrane bioreactor (MBR) treating sugarcane molasses based distillery wastewater (spentwash). The 8 L reactor was equipped with a submerged 30 μm nylon mesh filter with 0.05 m² filtration area. Detailed characterization of the commercial wood charcoal based PAC was performed before using it in the MBR. The MBR was operated over 200 days at organic loading rates (OLRs) varying from 4.2 to 6.9 kg m⁻³ d⁻¹. PAC addition controlled the reactor foaming during start up and enhanced the critical flux by around 23%; it also prolonged the duration between filter cleaning. Operation at higher loading rates was possible and for a given OLR, the chemical oxygen demand (COD) removal was higher with PAC addition. However, biodegradation in the reactor was limited and the high molecular weight compounds were not affected by PAC supplementation. The functional groups on PAC appear to interact with the polysaccharide portion of the sludge, which may reduce its propensity to interact with the nylon mesh.     

Stabilization/solidification (S/S) of mercury-containing wastes using reactivated carbon and Portland cement

Stabilization/solidification (S/S) of mercury-containing solid wastes using activated carbon and cement was investigated in this study. The activated carbon used in the study was a powder reactivated carbon (PAC). The effect of sulfur-treatment of the PAC was also studied. It was found that PAC was effective in stabilizing Hg in the waste surrogate. Pretreatment of the PAC by soaking it in CS(2) significantly improved the mercury adsorption capacity of the PAC. The adsorption equilibrium was reached within 24h. The optimum pH for the reaction was within the range of 5.0-5.5. After mercury stabilization by adsorption on the reactivated carbon, the Hg waste surrogate was mixed with Portland cement for solidification. Surrogates with up to 1000 mg/kg Hg were stabilized and solidified well enough to pass the TCLP test. The adsorption of mercury by reactivated carbon was in accordance with the Freundlich isotherm. Cement solidification of reactivated carbon-stabilized surrogates, significantly reduced the often-reported interference by chloride ions, by forming a barrier outside of the carbon particles. The S/S process using reactivated carbon and cement is an effective and economical technology for treating and disposing mercury-containing solid wastes.     

Fenton's peroxidation and coagulation processes for the treatment of combined industrial and domestic wastewater

As a consequence of the population growth, major efforts have been made by the Egyptian government to construct new industrial areas. Tenth of Ramadan City is one of the most important industrial cities in Egypt. The wastewater generated from various industrial activities was highly contaminated with organic matters as indicated by COD (1750-3323 mg/L), TSS (900-3000 mg/L) and oil and grease (13.2-95.5 mg/L). All overall appraisals of the analytical data from the industrial wastewater indicate that pretreatment is required for all industrial sectors to achieve compliance with the Egyptian Environmental law which requires effective pretreatment of industrial wastewater prior to its discharge into public sewers. Treatability studies via conventional and Fenton processes have been investigated. The efficiency of conventional treatment methods led to 63% COD and 44% color removal by using FeCl(3) as coagulant. Various coagulant aids and powdered activated carbon (PAC) were added to 400mg/L FeCl(3) in order to enhance the removal of color. It was found that polyacrylamide polymer, bentonite and PAC increased the efficiency of the treatments where the color removal increased to 79%, by cationic polymer, 73% by anionic polymer, 84.5% by bentonite and 95% for 0.4 g/L PAC. Fenton process was investigated which under the operating conditions (pH 3.0+/-0.2, Fe(2+) dose=400 mg/L and H(2)O(2)=550 mg/L), color removal up to 100% and more than 90% of COD removal were achieved.     

粉末活性炭-超滤膜联用去除水体藻类

针对日益严重的水体藻类污染问题,分别选用粉末活性炭(PAC)、超滤(UF)及其组合工艺对富藻水体藻类物质(铜绿微囊藻)去除特性进行研究.实验结果表明,单独的粉末活性炭工艺即使在高投加量情况下(PAC投加量为120 mg/L)对藻类物质去除效果不佳;单独的超滤膜工艺虽然对藻类物质有较好的去除效果(去除率达到95％),但是...     

Effect of PAC addition on immersed ultrafiltration for the treatment of algal-rich water

The aim of this study was to evaluate the effect of powdered activated carbon (PAC) addition on the treatment of algal-rich water by immersed ultrafiltration (UF), in terms of permeate quality and membrane fouling. Experiments were performed with a hollow-fiber polyvinyl chloride ultrafiltration membrane at a laboratory scale, 20-25°C and 10 L/(m(2) h) constant permeate flux. UF could achieve an absolute removal of Microcystis aeruginosa cells, but a poor removal of algogenic organic matter (AOM) released into water, contaminants responsible for severe membrane fouling. The addition of 4 g/L PAC to the immersed UF reactor significantly alleviated the development of trans-membrane pressure and enhanced the removal of dissovled organic carbon (by 10.9±1.7%), UV(254) (by 27.1±1.7%), and microcystins (expressed as MC-LR(eq), by 40.8±4.2%). However, PAC had little effect on the rejection of hydrophilic high molecular weight AOM such as carbohydrates and proteins. It was also identified that PAC reduced the concentrations of carbohydrates and proteins in the reactor due to decreased light intensity, as well as the MC-LR(eq) concentration by PAC adsorption.     

Development of parthenium based activated carbon and its utilization for adsorptive removal of p-cresol from aqueous solution

The activated carbon was prepared from carbonaceous agriculture waste Parthenium hysterophorous by chemical activation using concentrated H2SO4 at 130+/-5 degrees C. The prepared activated carbon was characterized and was found as an effective adsorbent material. In order to test the efficacy of parthenium based activated carbon (PAC), batch experiments were performed to carryout the adsorption studies on PAC for the removal of highly toxic pollutant p-cresol from aqueous solution. The p-cresol adsorption studies were also carried out on commercial grade activated carbon (AC) to facilitate comparison between the adsorption capabilities of PAC and AC. For PAC and AC, the predictive capabilities of two types of kinetic models and six types of adsorption equilibrium isotherm models were examined. The effect of pH of solution, adsorbent dose and initial p-cresol concentration on adsorption behaviour was investigated, as well. The adsorption on PAC and on AC was found to follow pseudo-first order kinetics with rate constant 0.0016 min(-1) and 0.0050 min(-1), respectively. The highest adsorptive capacity of PAC and AC for p-cresol solution was attained at pH 6.0. Further, as an adsorbent PAC was found to be as good as AC for removal of p-cresol upto a concentration of 500 mg/l in aqueous solution. Freundlich, Redlich-Peterson, and Fritz-Schlunder models were found to be appropriate isotherm models for PAC while Toth, Radke-Prausnitz and Fritz-Schlunder were suitable models for AC to remove p-cresol from aqueous solution.     

Consequence of chitosan treating on the adsorption of humic acid by granular activated carbon

In this work, equilibrium and kinetic adsorption of humic acid (HA) onto chitosan treated granular activated carbon (MGAC) has been investigated and compared to the granular activated carbon (GAC). The adsorption equilibrium data showed that adsorption behaviour of HA could be described reasonably well by Langmuir adsorption isotherm for GAC and Freundlich adsorption isotherm for MGAC. It was shown that pre-adsorption of chitosan onto the surface of GAC improved the adsorption capacity of HA changing the predominant adsorption mechanism. Monolayer capacities for the adsorption of HA onto GAC and MGAC were calculated 55.8 mg/g and 71.4 mg/g, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process for MGAC.     

Adsorption characteristics of haloacetonitriles on functionalized silica-based porous materials in aqueous solution

The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based porous materials was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm models were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS.     

Effects of adsorbents and copper(II) on activated sludge microorganisms and sequencing batch reactor treatment process

Wastewater treatment systems employing simultaneous adsorption and biodegradation processes have proven to be effective in treating toxic pollutants present in industrial wastewater. The objective of this study is to evaluate the effect of Cu(II) and the efficacy of the powdered activated carbon (PAC) and activated rice husk (ARH) in reducing the toxic effect of Cu(II) on the activated sludge microorganisms. The ARH was prepared by treatment with concentrated nitric acid for 15 h at 60-65 degrees C. The sequencing batch reactor (SBR) systems were operated with FILL, REACT, SETTLE, DRAW and IDLE modes in the ratio of 0.5:3.5:1:0.75:0.25 for a cycle time of 6 h. The Cu(II) and COD removal efficiency were 90 and 85%, respectively, in the SBR system containing 10 mg/l Cu(II) with the addition of 143 mg/l PAC or 1.0 g PAC per cycle. In the case of 715 mg/l ARH or 5.0 g ARH per cycle addition, the Cu(II) and COD removal efficiency were 85 and 92%, respectively. ARH can be used as an alternate adsorbent to PAC in the simultaneous adsorption and biodegradation wastewater treatment process for the removal of Cu(II). The specific oxygen uptake rate (SOUR) and kinetic studies show that the addition of PAC and ARH reduce the toxic effect of Cu(II) on the activated sludge microorganisms.     

Effects of Powder Activated Carbon Particle Size on Activated Carbon Monolith's Properties

Methyl cellulose as organic binder and bentonite as clay binder were simultaneously used to prepare activated carbon monolith (ACM) using powder activated carbon (PAC) and by means of extrusion process. To study the effects of PAC particle size on porosity, adsorption, and mechanical properties of the ACMs, four broad types of PAC including powder with particle size less than 150, 90, 50 µm, and powder without screening were prepared and used. Actually, it was tried to improve the adsorption capacity, surface area, and mechanical strength (both compression and impact strength) of the ACMs by screening the PAC microparticles to certain particle sizes. The results showed that arranging and decreasing the PAC particle size significantly improved the above-mentioned properties.     

Biomimetic fat cell (BFC) modification and for lindane removal from aqueous solution

To improve the regeneration ability of biomimetic fat cell (BFC), an innovative agent for hydrophobic organic contaminants (HOCs) removal, BFC was modified through introducing 1, 3, 5-benzenetricarboxyl trichloride with trifunctional group and heterocyclic piperazine in this research. Modified biomimetic fat cell (MBFC) has a good lindane removal capacity close to that of BFC and powder activated carbon (PAC), and the lindane removal is 97.68, 96.65 and 98.36% with 7 mg/L lindane initial concentration, respectively. At the same time, 20 mg/L MBFC or PAC is sufficient for 10 microg/L lindane removal, and in 20-60 mg/L doses range the lindane removal by both MBFC and PAC can reach 99.0%; When the doses is below 10 mg/L, MBFC showed better lindane removal than PAC and MBFC even could reach 96.8% lindane removal in 5 mg/L dose. Lindane removal by MBFC could be held on 95% above in first 6-time reuse. Though the lindane removal by MBFC decreased with the reuse time increasing, MBFC still could remove 80 % lindane after 9 times regeneration. In contract with BFC, MBFC showed obvious advantage on the regeneration. The lindane removal mechanism by MBFC, similar with BFC, includes bioaccumulation by MBFC nucleolus-triolein and adsorption by MBFC membrane, and the bioaccumulation is the main way.     

Potential method to improve the treatment efficiency of persistent contaminants in industrial wastewater

The objective of this work was to evaluate a potential method for improving the treatment efficiency of persistent contaminants in industrial wastewater. Adsorption with powdered activated carbon (PAC) was applied as pre-treatment and operational conditions as pH, temperature, carbon concentration and time were investigated in laboratory scale for different streams generated in a fine chemical industry. Chemical oxygen demand (COD) removal efficiencies of 63 and 50% were attained for two important industrial streams, Product C after acid treatment and precipitation and Influent, at pH 7, room temperature and with 5 and 15 g l(-1) of PAC, respectively. Biodegradation assays showed that PAC adsorption enhanced COD removal efficiency. PAC pre-treatment increased the COD removal of Product C after production stream from 15 to 80% and improved the biodegradability of the Influent stream by 50%.     

Comparisons of adsorbent cost for the removal of zinc (II) from aqueous solution by carbon nanotubes and activated carbon

The reversibility of Zn2+ sorption onto single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and powdered activated carbon (PAC) was investigated to evaluate their repeated availability performance in water treatment. Under the same conditions, the Zn2+ sorption capacity of SWCNTs and MWCNTs was more than that of PAC and could be maintained after several cycles of water treatment and regeneration. A statistical analysis on the replacement cost of these adsorbents based on the best-fit regression of the measured equilibrium capacity of each water treatment cycle was also conducted. The results revealed that the SWCNTs and MWCNTs could be reused through a large number of water treatment cycles and thus appear cost-effective in spite of their high unit cost at the present time.     

Modelling Cr(VI) removal by a combined carbon-activated sludge system

The combined carbon-activated sludge process has been proposed as an alternative to protect the biomass against toxic substances in wastewaters; however, the information about the effect of powdered-activated carbon (PAC) addition in activated sludge reactors for the treatment of wastewaters containing Cr(VI) is limited. The objectives of the present study were: (a) to evaluate the removal of hexavalent chromium by (i) activated sludge microorganisms in aerobic batch reactors, (ii) powdered-activated carbon, and (iii) the combined action of powdered-activated carbon and biomass; (b) to propose mathematical models that interpret the experimental results. Different Cr(VI) removal systems were tested: (S1) biomass (activated sludge), (S2) PAC, and (S3) the combined activated carbon-biomass system. A Monod-based mathematical model was used to describe the kinetics of Cr(VI) removal in the system S1. A first-order kinetics with respect to Cr(VI) and PAC respectively, was proposed to model the removal of Cr(VI) in the system S2. Cr(VI) removal in the combined carbon-biomass system (S3) was faster than both Cr(VI) removal using PAC or activated sludge individually. Results showed that the removal of Cr(VI) using the activated carbon-biomass system (S3) was adequately described by combining the kinetic equations proposed for the systems S1 and S2.     

Removal of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans by three coagulants in simulated coagulation processes for drinking water treatment

Surface water from Guangzhou to which standard polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were added was treated by coagulation with ferric chloride (FC), polyaluminium chloride (PAC), and aluminium sulfate (AS) at optimum removal dosages for nature organic matter (NOM) to assess the polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) removal efficiencies. PCDD/Fs in suspended particulate matter (SPM) and treated water (TW) after coagulation were analysed. Low residual levels of PCDD/Fs were found in treated water after coagulation: 0.8% for FC, 0.9% for PAC, and 3.1% for AS. The removal efficiency calculated using these results was >99% for FC and PAC and 97-98% for AS. Most PCDD/Fs congeners could be removed by the three coagulation processes; the removal efficiency of FC and PAC was similar, and slightly higher than that of AS. The results also demonstrate that coagulation with FC preferentially removed tetra- and penta-substituted PCDD/Fs from raw water.