Granulated Activated Carbon Research Articles

Mathematical Models for Removal of Pharmaceutical Pollutants in Rehabilitated Treatment Plants

This paper aims to investigate appropriate mathematical models devoted to the optimization of some cleaning processes related to pharmaceutical contaminant removal. In our recent works, we found the rehabilitation of the existing cleaning plants as a viable solution for the removal of this type of micropollutants from waters by introducing efficient techniques such as adsorption on granulated active carbon filters and micro-, nano-, or ultrafiltration. To have these processes under better control and to assure the transfer from small- to large-scale treatment stations, specific mathematical models are necessary. Starting from Navier–Stokes equations and imposing proper boundary conditions, some mathematical physics problems are obtained for which adequate solving methods via variational methods and surjectivity results are proposed. The importance of these solution characterizations consists in their continuation in adequate numerical methods and the possibility to visualize the result by using a CFD program.

Purification of industrial toluene from technical to reagent grade using Diahope activated carbon in a pilot-scale fixed-bed column

The removing organic impurities from technical-grade toluene (99.1 %) to produce reagent-grade toluene (99.9 %) has been addressed by assessing the mono- and multi-component adsorption of methylbenzothiophene (MBT), ethylcyclopentane (ECP), and xylene (XYL), which represent sulfur, non-aromatic, and aromatic impurities, respectively. Laboratory-scale static-experiments conducted between 10 and 30 °C showed that although toluene sorption on granulated activated carbon (GAC) is exothermic, the sorption capacity for each impurity increased with temperature, indicating endothermic sorption for the impurities. The sorption behavior for MBT and ECP followed the Langmuir model while for XYL followed the Freundlich model with the order of sorption affinity as MBT > ECP > XYL. In pilot-scale dynamic-experiments, the breakthrough curves (BTCs) were evaluated under various bed heights (60 and 120 cm), flow rates (1–3 L min−1), sorbate inlet concentrations (200–400 mg L−1), and optimal temperature (30 °C) obtained in static experiments. In mono-component sorption, the highest sorption capacities for MBT, ECP, and XYL were 97.1, 70.7, and 65.4 mg g−1, respectively, while the corresponding values were 46.0, 43.0, and 22.9 mg g−1 respectively, in multi-component sorption under the same operating conditions. A CFD simulation in COMSOL (v.6.2) revealed sharper BTCs with time delay compared to the experimental data while a good correlation (R2 > 0.99) was observed for BT models. The narrower mass transfer zone for MBT and ECP compared to XYL indicated more effective sorption of these sorbates, respectively. Regenerating GAC up to four cycles with hot N2 (80 °C) showed a satisfactory sorption capacity for industrial toluene impurities, indicating a reversible sorption–desorption process with a cumulative sorption usage rate of 5.5 g L−1. The pilot-scale set-up used in this study successfully purified a large volume (∼475 L) of industrial toluene.

Vesicles exhibit high-performance removal of per-and polyfluoroalkyl substances (PFAS) depending on their hydrophobic groups

The removal of per- and polyfluoroalkyl substances (PFAS) from drinking water is urgently needed. Here, we demonstrated high performance of vesicles on PFAS adsorption. Vesicles used in this study were enclosed amphiphile bilayers keeping their hydrophobic groups inside and their hydrophilic groups outside in water. The distribution coefficient Kd of perfluorooctane sulfonic acid (PFOS) for vesicles was 5.3 × 105 L/kg, which is higher than that for granulated activated carbon (GAC), and Kd of perfluorooctanoic acid (PFOA) for vesicles was 103–104 L/kg. The removal efficiencies of PFOA and PFOS adsorption on DMPC vesicles were 97.1 ± 0.1% and 99.4 ± 0.2%, respectively. The adsorption behaviors of PFOA and PFOS on vesicles were investigated by changing the number of cis-double bonds in the hydrophobic chains of the vesicle constituents. Moreover, vesicles formed by membranes in the different phases were also tested. The results revealed that, when vesicles are formed of a membrane in the liquid-crystalline (liquid-like) phase, the adsorption amounts of both PFOA and PFOS increased as the cis-double bond in the hydrocarbon chains decreased, which is considered due to molecular shape similarity. When vesicles are formed of a membrane in the gel (solid-like) phase, they do not adsorb PFAS as much as in the liquid-crystalline phase, even though the hydrocarbon chains do not have any cis-double bond. Our findings demonstrate that vesicles can be utilized as PFAS adsorbents by optimizing the structure of vesicle constituents and their thermodynamical phase. Indeed, the vesicles (DMPC) were demonstrated that they can adsorb PFOA and PFOS, and be coagulated by a coagulant even in environmental water. The coagulation will enable the removal of PFOA and PFOS from the water after adsorption.

Fabric- and film-structured supercapacitor

Supercapacitors had gained much interest due to their high power density, long cycle life, and fast charge and discharge speed. However, traditional supercapacitors were commonly produced with rigid structures and liquid electrolytes that cause many limits in flexible and non-traditional end uses. Although liquid electrolytes can be replaced by polymer-based gel electrolytes, time-dependent high stiffness, and capacitance loss were found to be the main drawbacks. Herein, an all-solid-state supercapacitor based on fabric/film composition was studied. Activated carbon granule (ACG) was used as an electrode material and polyvinyl alcohol (PVA) with phosphorous acid was selected as both polymer matrix and electrolyte. The as-prepared supercapacitor exhibited the typical double-layer electrostatic capacitive behavior, showing a good specific capacitance of 0.998 mF cm−2 at the scan rate of 10 mV s−1. When ZnO nanoparticles were added, the supercapacitor was further enhanced, showing a better specific capacitance of 1.321 mF cm−2 at the scan rate of 10 mV s−1. The supercapacitor was capable of bending at any angle without suffering its performance. This result indicated that the fabricated supercapacitor structure was flexible, lightweight, and capable of being integrated into textile products.

Biotesting for adsorptive bioremediation of oil-contaminated podzolic soil in Western Siberia

The majority of Russia’s oil and gas-producing regions are situated in the northern part of Western Siberia, where sandy podzolic soils are prevalent. Due to the low buffering capacity of these soils and the severe Arctic climate, the conventional method of bioremediation for removing oil contamination is not effective. This study, for the first time, explores the potential of adsorptive bioremediation for purifying oil-polluted gley-podzolic soil. This approach involves introducing natural sorbents of various classes before soil treatment through bioremediation. The optimal conditions for soil treatment can be determined using the express phytotests based on white clover ( Trifolium repens ) seed germination. The results indicate that under the best conditions, which involve adding 2 % mixed sorbent based on granulated activated carbon (GAC) and diatomite (4:1) or Spilsorb, it is possible to minimize soil phytotoxicity after 2-3 warm seasons and reduce the content of total petroleum hydrocarbons to the permissible residual oil content (≤5 g/kg) established in the territory of the Khanty-Mansiysk Autonomous Okrug for recultivated agricultural soils. Moreover, other sorbents, such as peat, GAC, vermiculite, zeolite, and diatomite, can be used to reduce phytotoxicity to <33 %, allowing for additional soil decontamination through phytoremediation.

Erratum to: Adsorption of Manganese(II) from Aqueous Solution by Activated Carbon Granules

Erratum to: Adsorption of Manganese(II) from Aqueous Solution by Activated Carbon Granules

The effect of activated carbon granules and KOH solution on welding particulates and gases in air filtration

Hazard Identification Risk Assessment Risk Control (HIRARC) is the process of identifying hazards that can occur in routine or non-routine activities in a company or workplace, then carrying out a risk assessment of these hazards.And from the risk assessment, the hazards in the welding workshop that have a moderate risk and are interesting for researchers to innovate are from sources of danger caused by smoke resulting from welding activities, causing workers to experience respiratory problems and eye irritation. Researchers created a smoke filtration device generated from welding with a system where the welding smoke is channeled into the KOH solution to reduce the number of air particles and reduce the levels of toxic substances in the welding smoke, then to keep the KOH solution always clean, a circulation system was created through the carbon to removes dirt and keeps the solution water from being dirty and colorless.Once all the tools are ready, measurements can be made to measure several chemical elements in the welding smoke from the point before it enters the filter and after going through the filtration process. Among the elements measured are Carbon Dioxide (CO 2), Carbon Monoxide (CO), Particulate PM 2.5 (2.5 Microns), and Particulate PM 10 (10 Microns). Based on research and data testing carried out using the Anova Test and Fisher Pairwise Comparisons, it can be concluded that to produce the best and cleanest air results, the composition is K4 C1 or KOH 10% with Cabon Active 2-3 Mesh. Because if activated carbon with a mesh size larger than 2-3 mesh will affect the quality of the KOH solution because the granules are too small and contaminate the KOH solution. And the higher the KOH solution level, the more effective it is at reducing the dangerous elements in welding fumes.

Life cycle analysis and economic evaluation of adsorptive removal of arsenic from groundwater using GAC and GAC-Fe adsorbents

The potential health effects associated with consumption of arsenic contaminated water have motivated chemical and energy intensive treatment processes. Granulated activated carbon (GAC) and iron impregnated granular activated carbon (GAC-Fe) are the two adsorbents which have shown significant removal of arsenic (As(V)). However, the synthesis of different adsorbents involves significant different materials and energy interactions which have different environmental and economic burdens. This study evaluates and compares the environmental impacts arising from treatment of arsenic containing water using GAC and GAC-Fe adsorbents, for the selection of more suitable one. The life cycle inventory pertaining to treatment through two adsorbents was prepared based on the data available in literature. The impacts were assessed utilizing ‘Sphera LCA for experts’ software with three midpoint methods i.e. CML 2001, TRACI 2.1 and ReCiPe 2016. Results show that chemically treated/impregnated adsorbents for arsenic contaminated water treatment not only have lesser environmental emissions but also reduces the treatment cost. The treatment with GAC-Fe has ∼30% lower impacts in GWP, AP, EP, MAETP, FAETP, ODP, ADP (E) and HTP categories than treatment with GAC, since increase in adsorbent's specific uptake in GAC-Fe reduces the amount of total adsorbent requirement. GAC-Fe based water treatment costs ∼23% less than with GAC. The main responsible parameters for emissions are synthesis of GAC from hard coal precursor, and electricity consumption in carbonization and drying operations. Apart from this, in case of GAC-Fe, additional impregnation and drying operation also contributes to emissions. The utilization of coke oven gas generated in adsorbent synthesis for energy credits has potentially reduced the emissions and operating cost. The less standard deviation (<10%) in Monte Carlo (MC) uncertainty analysis, indicated the reliability and robustness of LCA impacts. This study exemplified the environment friendliness of metal impregnated GAC based arsenic contaminated water treatment.

Ecotoxicological mixture risk assessment of 35 pharmaceuticals in wastewater effluents following post-treatment with ozone and/or granulated activated carbon

Reducing the risk posed by mixtures of pharmaceuticals is a goal of current initiatives such as the European Green Deal to reduce anthropological environmental impacts. Wastewater effluent typically contains large numbers of active pharmaceutical ingredients (APIs). For some APIs, existing technology such as conventional activated sludge (CAS) wastewater treatment plants (WWTPs) have removal rates below 20 %, thus the WWTP discharges are adding to the toxic burden of receiving waters.We present an environmental risk assessment of mixtures of 35 APIs in effluent samples from 82 Northern European WWTPs using the concentration addition model, and identify the respective risk-driving APIs. This is then compared to a corresponding mixture risk assessment of effluent samples from the Danish Hillerød WWTP subjected to post-treatment with varying specific ozone doses (0.15–1.05 mgO3/mgDOC) and/or granulated activated carbon (GAC).All 82 WWTP effluent samples exceeded risk thresholds by at least a factor of 30, with a median RQSUM of 92.9, highlighting the need for effluent post-treatment and/or a substantial dilution in the recipient waters. Antibiotics, analgesics and anti-depressants were among the top risk drivers with 99 % of the average mixture risk attributable to azithromycin, diclofenac, venlafaxine, clarithromycin and mycophenolic acid. Effluent mixture risk was reduced by ozonation in a concentration-dependent manner, decreasing below threshold levels to a median RQSUM of 0.83 following treatment with 0.65 mgO3/mg DOC. Fresh GAC was also effective at reducing the mixture risk both alone and with ozone treatment, with median RQSUM of 0.04 and 0.07 respectively.To our knowledge, this is the first study to present a risk assessment of pharmaceutical mixtures in effluent comparing “conventional” WWTP processes with additional post-treatment with ozone and/or GAC for reducing the joint risks of pharmaceutical mixtures for recipient waters. We demonstrate the need for additional WWTP treatment technologies, and the efficacy of GAC and ozonation in decreasing the risk to the aquatic environment from pharmaceutical mixtures to below acceptable threshold limits.

Sorption of Halogenated Anti-Inflammatory Pharmaceuticals from Polluted Aqueous Streams on Activated Carbon: Lifetime Extension of Sorbent Caused by Benzalkonium Chloride Action

The enhancement of the adsorption capacity of activated carbon (AC) using benzalkonium chloride (BAC) within the adsorption of halogenated pharmaceuticals flufenamic acid (flufa) and diclofenac (dcf) was investigated in this study. An adsorption kinetic study was performed to evaluate the adsorption mechanisms. The adsorption mechanism of both drugs on granulated AC as well as saturated AC activated by BAC can be evaluated via pseudo-second kinetic order. The equilibrium adsorption capacity of spent granulated AC in co-action with BAC (qflufa = 195.5 mg g−1 and qdcf = 199.5 mg g−1) reached the adsorption capacity of virgin granulated AC (qflufa = 203.9 mg g−1 and qdcf = 200.7 mg g−1). Finally, batch and column arrangements were compared in an effort to possible practical application of exhausted AC in co-action with BAC. In both column and batch experiments, adsorption capacities of spent granulated AC for flufa increased using BAC by 170.4 mg g−1 and 560.4 mg g−1, respectively. The proposed mechanism of adsorption enhancement is the formation of less polar ion pairs and its better affinity to the non-polar AC surface. The drug concentrations were determined using the voltammetric method on carbon paste electrodes. The formation of ion pairs has been studied by the H1 NMR technique, and solubility in water of drugs and respective ion pairs were investigated using octan-1-ol/water coefficients (POW).

Separation of VOC Gaseous Mixtures Using an Adsorption–Desorption Device

The aim of this work was to separate ethanol in an experimental adsorption–desorption device. We focused on concentrating ethanol by adsorption onto granulated activated carbon in its gaseous phase, which was produced by stripping a matrix with different ethanol concentrations (2, 5, 10, and 15% v/v). For adsorption, three kinds of granulated activated carbon (GAC) were used, marked as GAC1, GAC2, and GAC3. The separation product had a higher ethanol concentration than the initial ethanol concentration before the adsorption–desorption process. The enrichment factor was, in the case of the initial ethanol concentration, 2% v/v at the level of 10. With our new adsorption–desorption device, it is possible to achieve a product with an ethanol concentration of 59.0% v/v with stripping, adsorption, desorption, and condensation. To verify the separation efficiency, a real matrix (fermentation broth) was used. The ethanol concentration in the real matrix was, at the beginning of the separation process, 0.65% v/v; after using our separation device, it was 11.35% v/v. Using a real matrix, the enrichment factor was at the level of 18. The main advantage is the use of our new adsorption–desorption device for the continuous separation of ethanol from fermentation broth. A mathematical model was created, based on which it is possible to calculate the ethanol concentration in the product of the separation process with high accuracy.

Engineering a biofilters microbiome with activated carbon and bioaugmentation to improve stormwater micropollutant removal

Harnessing prokaryotes’ metabolic capacity and adaptive potential is of interest for environmental bioremediation and biological treatment of domestic and industrial waste. Bioaugmentation is commonly implicated in the cleanup of high-dosed environmental pollution. In this study, Arthrobacter aurescens TC1 was used to augment biofiltration systems for bioremediation of stormwater micropollutant. Bioaugmentation was tested on non-vegetated and vegetated system designs, with or without an adsorbent biocarrier [granulated activated carbon (GAC)]. This study investigated how system design affects microbial function and structure. It focused on long-term metabolic responses of the biofilter’s microbiome to low chronic exposure to the herbicide atrazine and fluctuations in atrazine load. Shotgun metagenomics analyses demonstrated that the major contributor to microbiome structure was the supplementation of GAC. Vegetation affected microbiome structure mainly in sand biofilter-media. GAC showed a significant shift in atrazine-degrading genes over time compared to sand. Diversity and richness increased with time in all system designs, regardless of atrazine load fluctuations. To conclude, incorporating GAC in stormwater-biofiltration systems effectively enhances the micropollutant-biodegradation capacity in stormwater with negligible effects on the biofilter’s microbiome diversity and function.

Transport and removal of stormwater vehicle-related mobile organic contaminants in geomedia-amended sand columns

Green infrastructure drainage systems are innovative treatment units that capture and treat stormwater. Unfortunately, highly polar contaminants remain challenging to remove in conventional biofilters. To overcome treatment limitations, we assessed the transport and removal of stormwater vehicle-related organic contaminants with persistent, mobile, and toxic (in short: PMTs) properties, such as 1H-benzotriazole, NN'-diphenylguanidine, and hexamethoxymethylmelamine (PMT precursor), using batch experiments and continuous-flow sand columns amended with pyrogenic carbonaceous materials, like granulated activated carbon (GAC) or wheat-straw derived biochar. Our results indicated that all investigated contaminants were subjected to nonequilibrium interactions in sand-only and geomedia-amended columns, with kinetic effects upon transport. Experimental breakthrough curves could be well described by a one-site kinetic transport model assuming saturation of sorption sites, which we inferred could occur due to dissolved organic matter fouling. Furthermore, from both batch and column experiments, we found that GAC could remove contaminants significantly better than biochar with higher sorption capacity and faster sorption kinetics. Hexamethoxymethylmelamine, with the lowest organic carbon-water partition coefficient (KOC) and largest molecular volume among target chemicals, exhibited the lowest affinity in both carbonaceous adsorbents based on estimated sorption parameters. Results suggest that sorption of investigated PMTs was likely driven by steric and hydrophobic effects, and coulombic and other weak intermolecular forces (e.g., London–van der Waals, H-bonding). Results from extrapolating our data to a 1-m depth geomedia-amended sand filter suggested that GAC and biochar could enhance the removal of organic contaminants in biofilters and last for more than one decade. Overall, our work is the first to study treatment alternatives for NN'-diphenylguanidine and hexamethoxymethylmelamine, and contributes to better PMT contaminant removal strategies in environmental applications.

Formaldehyde Reduction in an Operating Room Setting: Comparison of a Catalytic Surgical Vacuum Device With a Traditional Smoke Evacuator.

Introduction Electrosurgery exposes healthcare workers to volatile organic compounds (VOCs) including formaldehyde. Adopting electrosurgical devices that catalytically transform formaldehyde to benign substances has the potential to improve safety in surgical settings. Materials and methods We compared the efficiency of formaldehyde removal of two medical devices.The first was a novel surgical vacuum (SV) device containing ultra-low particulate air (ULPA) filtration, activated carbon and catalytic transition metal oxide.The second was a commonly utilized handpiece evacuator (HE) that contained only mechanical filtration and activated carbon granules. Both devices were exposed to formalin vapor. Results The time weighted average (TWA), median and peak concentrations of detected formaldehyde at the outflow of the SV unit were 90% lower than the corresponding values detected at the outflow of the HE device (p = 0.0034). When catalytic material was added to the HE device, the detected formaldehyde concentration at the outflow was reduced by 55%(p = 2.9 x 10-15). Conclusions The catalytic SV device has the potential to considerably reduce formaldehyde levels in operating room (OR) environments.

Production of Shaped Activated Carbon Granules Using Binder Derived from Heavy Petroleum Tar

Production of Shaped Activated Carbon Granules Using Binder Derived from Heavy Petroleum Tar

The efficacy of soil washing for the remediation of per- and poly-fluoroalkyl substances (PFASs) in the field.

This paper aims to describe the performance of a soil washing plant (SWP) for remediating a per- and poly-fluoroalkyl substances (PFASs)-contaminated soil with a high clay content (61%). The SWP used both physical and chemical processes; fractionation of the soil particles by size and partitioning of PFASs into the aqueous phase to remove PFASs from the soil. Contaminated water was treated in series with granulated activated carbon (GAC) and ion-exchange resin and reused within the SWP. Approximately 2200t (dry weight) of PFAS-contaminated soil was treated in 25 batches of 90t each, with a throughput of approximately 11t soil/hr. Efficiency of the SWP was measured by observed decreases in total and leachable concentrations of PFASs in the soil. Average removal efficiencies (RE) were up to 97.1% for perfluorocarboxylic acids and 94.9% for perfluorosulfonic acids. REs varied among different PFASs depending on their chemistry (functional head group, carbon chain length) and were independent of the total PFAS concentrations in each soil batch. Mass balance analysis found approximately 90% of the PFAS mass in the soil was transferred to the wash solution and >99.9% of the PFAS mass in the wash solution was transferred onto the GAC without any breakthrough.

Optimization of the effect of microelectrodes on Ni2+ removal in three-dimensional electrode system.

This study investigated Ni+2 removal performance in 3DER reactors where electrocoagulation mechanisms and microelectrodes are used together. EDTA modification was carried out on the granule-activated carbon surface to increase the efficiency and affinity of microelectrodes against Ni+2 molecules. The grafting was examined using BET, FT-IR, SEM, EDS, and the elemental mapping methods. With the surface analyses made in this study, it was revealed that EDTA modification on granulated activated carbon was successfully performed. Also, 8.48%wt by mass of EDTA grafting on granular activated carbon was possible. EDTA functionalization did not affect the surface pore structures of CAC much. Under 10V potential, 97.82% Ni removal efficiency was obtained with 2D in 35min, while 96.69% removal in 10min and 100% removal in 15min were obtained in the 3D reactor. The Ni+2 removal mechanism in 3DER reactors has been determined to conform to the pseudo-second-order kinetic model. The k2 value obtained for 10V (1.36 10-2) is 27 times the k2 value obtained for 5V for 3DER reactors. In addition, using central composite design (CCD), operational parameters such as time, concentration, and potential difference affecting Ni+2 removal in 3DER reactors have been optimized. The most influential parameter is the applied voltage, followed by time and concentration. It has been determined that 3DER reactors using EDTA-modified microelectrodes are highly efficient and suitable for Ni+2 removal.

PRODUCTION TECHNOLOGY AND FILTERING PROPERTIES OF CARBON BLOCK CARTRIDGES

In the present paper, the information on the influence of various factors on the carbon block cartridges production technology and their potential impact on the properties of the finished product is presented. The possibilities of increasing the sorption-filtering efficiency of carbon block cartridges are presented. The technical and exploitation characteristics are influenced by the size of the mixture components granules, the physicochemical properties of active carbon and binder polymers, their ratio in the mixture, and the addition of bactericidal additives into the composition. The study of this topic is relevant, as evidenced by the analysis of the increasing number of publications on this matter over the past ten years. However, the production technology of carbon block cartridges is the know-how of manufacturing companies. This information is confirmed by the analysis of the technical characteristics of sixty carbon block cartridges from nine world manufacturers, whose products are WQA certified according to the NSF/ANSI 42 standard. The recommendations given by a number of authors on the size of activated carbon granules in the range from 40 to 120 mesh and polyethylene particles from 80 to 160 mesh with a flow rate of 1.4-3 g/10 min, can be taken as "reference points" in the development of extrusion mixtures with different components ratio. The following factors play an important role in obtaining effective cartridges: the quality of pre-extrusion mixing of the composition, its resistance to delamination during the “transition” from the mixer to the extruder loading zone, extrusion temperature regimes by zones, product cooling temperature, backpressure on the billet leaving the extruder. The information given in this article will be useful when producing new carbon block cartridges, improving the parameters of existing technologies, as well as in the research development of cartridges with new properties.

ADSORPTION OF IMPURITIES FROM IRRIGATION WASTEWATER USING ACTIVATED CARBON PRODUCED FROM SELECTED BIOMASS

Pollution from wastewater generated through irrigation has been a major challenge to environmental engineers (especially agricultural engineers) today, as a result of the contaminants and pollutants discharged due to the chemicals from the fertilizers used on crops and the discharge of sediments to surface water or groundwater. An approach to treating this wastewater necessitated the study on the preparation and production of activated carbon to serve as an adsorbent using groundnut shell for the treatment of wastewater from irrigation. Therefore, the aim of this study was to prepare activated carbon from groundnut shells for the treatment of irrigation wastewater. Wastewater samples were collected from Oke-Oyi irrigation scheme. The samples were analysed for initial physicochemical properties using the Food and Agriculture Organization of the United Nations (FAO) standard. Raw groundnut shells were collected from Ogbomoso. The initial analysis of the drainage water shows the water is highly alkaline and contains sulphate and nitrate above FAO benchmark values. The groundnut shells were grinded and sieved to obtain a 2 mm diameter particle size. The sample was carbonized at 400°C for 30 minutes and activated with 0.3M of phosphoric acid. The effects of temperature (20°C, 30°C and 40°C) and dosage of the activated carbon (1 g, 1.5 g, 2 g and 2.5 g), contact time (30 minutes, 1 hour, 1.5 hours, and 2 hours), and granulated activated carbon (GAC) on sulphate and nitrate removal were studied. The effect of the adsorbent on water pH was also studied. The characterization of the prepared AC and the determination of adsorption capacity were carried out. The surface morphological changes of the AC samples were investigated using a scanning electron microscope operated at 25 kV. Fourier Transform Infrared Spectroscopy (FTIR) was carried out to establish the functional groups present. At temperatures of 40°C, 30°C, and 20°C, the pH of the water decreased from 9.94 to 8.22, 8.22, and 8.26, respectively. The optimum dosage with 100% sulphate removal from wastewater (30 – 0.14 mg/l) was 2.5g at 20°C while the optimum dosage for nitrate removal (41.5 – 0.0813 mg/l) ranges between 1–2.5g at 20°C. The SEM analysis produced a well-developed porous surface on the micrograph of AC after chemical activation, which suggests improved removal of impurities when used. Therefore, the use of groundnut shells as feedstock for AC serves the dual purpose of good waste management and pollution treatment antidote.

Batch adsorption of herbicides from aqueous solution onto diverse reusable materials and granulated activated carbon

This study reports the kinetics and isotherms of the adsorption of five herbicides, MCPA, mecoprop-P, 2,4-D, fluroxypyr and triclopyr, from aqueous solutions onto a range of raw and pyrolysed waste materials originating from an industrial setting. The raw waste materials investigated demonstrated little capability for any herbicide adsorption. Granulated activated carbon (GAC) was capable of the best removal of the herbicides, with >95% removal observed. A first order kinetic model fitted the data best for GAC adsorption of 2,4-D, while a pseudo-first order model fitted the data best for GAC adsorption of fluroxypyr and triclopyr, indicating that adsorption was via physisorption. A pseudo-second order kinetic model fitted the GAC adsorption of MCPA and mecoprop-P, which is indicative of chemisorption. The adsorption of the herbicides in all cases was best described by the Freundlich model, indicating that adsorption occurred onto heterogeneous surfaces.