Basic characterization of Norwegian NOM samples — Similarities and differences

NOM (natural organic matter) samples, isolated by reverse osmosis (RO), and nine NOM samples, concentrated by low-pressure, low-temperature evaporation (EVA) from various origin in Norway, were characterized by different methods. The methods included elemental content of the freeze-dried samples (C, H, N, and O), elemental content of the redissolved samples (DOC, Na, Ca, Cu, Fe, and Mn), specific spectral absorbance at λ = 254 nm (A(254 nm)/DOC) and at λ = 436 nm (A(436 nm)/DOC), UV/Vis-spectra, specific fluorescence (excitation and emission spectra), proton capacity, Cu-complexation capacity, and content of hydrolysable amino acids and carbohydrates. In addition, chromatographic characterization by gel chromatography and reversed-phase chromatography was done. Studies on adsorption and flocculation abilities and the formation of trihalomethanes (THM) and organic halogens adsorbable on activated carbon (AOX) upon chlorination were also investigated. Comparison of the results showed that the samples were different according to the origin of the sample, isolation procedure, and time of sampling. The differences are not the same for all parameters used. Standardized procedures have to be applied to redissolve the organic material in water in order to compare data. For the samples investigated, it was shown that parameters like elemental analysis (H/C ratio), the specific spectral absorption in the UV range, proton capacity, complexation capacity and anionic particle charge, amount of hydrolysable amino acids and carbohydrates, adsorption behaviour on activated carbon, and the THM-FP are sensitive parameters to show differences concerning origin and isolation procedure.     

Characterization of natural organic matter from eight Norwegian surface waters: Proton and copper binding

As a part of the International NOM-Typing Project, proton and copper binding studies were conducted on ultrafiltered (>1000 dal.) and dialysed (>100 dal.) natural organic matter (NOM) samples from eight Norwegian Lakes. The NOM samples were similar with respect to proton and copper binding, although minor differences were observed among the samples of different origin. Slight variations occurred for seasonal changes and lime additions. The proton binding pK_a values grouped in three distinct classes: pK_a1 = 4.20–4.28; pK_a2 = 6.61–6.87; and pK_a3 = 9.27–9.8. The average total proton binding site concentration of the NOM samples was: 12.7 meq/g total organic carbon (TOC). Two binding sites were established for copper with average log K1 = 4.84 and log K2 = 7.17. The average site concentration for samples isolated by reverse osmosis (RO) was 0.56 μmol/mg C. Copper binding characteristics appear to be influenced by the method of sample isolation. For NOM isolated by low pressure evaporation (evap), binding site concentrations are smaller, conditional stability constants are higher, variability of the copper complexation capacity is smaller, and correlation with elemental composition (C, N, H) is better than in the case of NOM isolated by RO.     

Influence of alumina coating on characteristics and effects of SiO2 nanoparticles in algal growth inhibition assays at various pH and organic matter contents

Silica nanoparticles (NPs) belong to the industrially most important NP types. In a previous study it was shown that amorphous SiO(2) NPs of 12.5 and 27.0 nm are stable in algal growth inhibition assays and that their ecotoxic effects are related to NP surface area. Here, it was hypothesized and demonstrated that an alumina coating completely alters the particle-particle, particle-test medium and particle-algae interactions of SiO(2) NPs. Therefore, stability and surface characteristics, dissolution, nutrient adsorption and effects on algal growth rate of both alumina coated SiO(2) NPs and bare SiO(2) NPs in OECD algal test medium as a function of pH (6.0-8.6) and natural organic matter (NOM) contents (0-12 mg C/l) were investigated. Alumina coated SiO(2) NPs aggregated in all media and adsorbed phosphate depending on pH and NOM concentration. On the other hand, no aggregation or nutrient adsorption was observed for the bare SiO(2) NPs. Due to their positive surface charge, alumina coated SiO(2) NPs agglomerated with Pseudokirchneriella subcapitata. Consequently, algal cell density measurements based on cell counts were unreliable and hence fluorescent detection of extracted chlorophyll was the preferred method. Alumina coated SiO(2) NPs showed lower toxicity than bare SiO(2) NPs at concentrations ≥46 mg/l, except at pH 6.0. At low concentrations, no clear pH effect was observed for alumina coated SiO(2) NPs, while at higher concentrations phosphate deficiency could have contributed to the higher toxicity of those particles at pH 6.0-6.8 compared to higher pH values. Bare SiO(2) NPs were not toxic at pH 6.0 up to 220 mg/l. Addition of NOM decreased toxicity of both particles. For SiO(2) NPs the 48 h 20% effect concentration of 21.8 mg/l increased 2.6-21 fold and a linear relationship was observed between NOM concentration and effective concentrations. No effect was observed for alumina coated SiO(2) NPs in presence of NOM up to 1000 mg/l. All experiments point out that the alumina coating completely altered NP interactions. Due to the difference in surface composition the SiO(2) NPs, which had the smallest surface area, were more toxic to the alga than the alumina coated SiO(2) NPs. Hence, surface modification can dominate the effect of surface area on toxicity.     

Capillary zone electrophoretic studies on Norwegian surface water natural organic matter

Capillary zone electrophoresis (CZE) is a useful tool for the analysis of the electrophoretic behavior of anionic polyelectrolytes like humic substances. CZE was used to compare natural organic matter (NOM) with high ash content obtained by reverse osmosis (RO) and low temperature, low pressure evaporation (Ev.) from different Norwegian surface water sources. The quantitative relation between the resulting electrophoretic signals (peak height and area) and the carbon amount of the injected NOM samples was found linear. The NOM gave homogeneous signals in CZE, with a distribution of the detection signals around an average electrophoretic mobility (AEM) corresponding to the charge density distribution of the NOM, governed by the distribution of their molecular sizes and acidities. Like humic substances, NOM only appears as anions in capillary electrophoresis (CE), but the high ash content of these samples and the presence of metals strongly influenced their mobilities at lower pH. CZE could be used as a tool for the rapid evaluation of the average net charge and the molecular radius of the NOM at pH 5.1.     

Natural organic matter in drinking water — The “NOM-typing project”, background and basic characteristics of original water samples and NOM isolates

The complex nature of natural organic matter (NOM), and the impact of this matter on drinking water quality, necessitate international co-operative efforts. After several decades of struggle, many experienced NOM scientists world wide recognize the need for international sample references, or better yet, to work together on the same set of samples. The aim of the “NOM-typing project” was a multi-method characterization of a limited number of NOM samples, isolated from different water sources. The background of the project and the nature of the sampling sites are described here, and some data comparing the composition of the samples, before and after the isolation, are presented. The techniques used for isolation were reverse osmosis (RO) and evaporation (EVA). The NOM samples were isolated from eight different locations in the southern part of Norway. The nature of the corresponding catchments differs, however, all samples were from areas with no influence of agriculture or local industry. The key issue of the project was that all samples were isolated with exactly the same methods and by the same team. In spite of the uniformity of the isolation technique used for the nine samples, the recoveries of the material differ from sample to sample. Generally, the loss of NOM is in the range of 10%, however, for one sample, the loss was as high as 35%. These discrepancies are probably partly because of differences in the nature of the NOM and partly due to differences in the general composition of the ambient water. There are a few remarkable differences between the nine samples. There was a high percentage of ash in isolates from acidified areas. These are also the samples where the loss of NOM during the isolation process was highest. The density of the RO-isolates differs 10-fold between the samples. The lipophilisity of the NOM samples, expressed as relative solubility in octanol, differs more than 30-fold.     

Isolation of natural organic matter — The influence on the assimilable organic carbon

The biofilm formation potential (BFP), determined by the assimilable organic carbon (AOC), was measured in water samples containing natural organic matter (NOM), and in “identical” samples reconstructed from NOM isolated by reverse osmosis (RO) and dissolved in distilled water. The results showed identical BFP in natural and reconstructed NOM water samples within the standard deviation of the AOC measurements. These results indicate that the composition of the NOM is the single most important parameter for the BFP of natural waters, and that the RO isolation of NOM produces a powder which, after dissolution in distilled water, is representative for the natural water containing NOM with regard to BFP determined by AOC.     

Characterization of natural organic matter from eight Norwegian surface waters: The effect of ash on molecular size distributions and CHN content

Natural organic matter (NOM) was isolated by reverse osmosis (RO) from eight surface waters in southern Norway. The freeze-dried samples were reconstituted in deionized water and part of the sample was dialysed against HCl. Samples of both the dialysed and non-dialysed materials were then ultrafiltered to give fractions: >50 000 dal., <50 000 but >10 000 dal. and <10 000 dal. nominal molecular weights (NMW). Dialysis against acid reduced the ash content of the samples by 68±14%. Non-dialysed NOM has a preponderance of carbon in the largest fraction (52.7±30%), while after dialysis, the smallest fraction of NOM has the greatest carbon content (52.2±9.7%). In addition to altering the overall apparent size distributions of the NOM fractions, dialysis generally reduces the amount of nitrogen relative to carbon in the NOM samples. The latter observation appears to be the result of losses of small molecular size organic matter that is enriched in nitrogen.     

Basic characterization of reference NOM from Central Europe — Similarities and differences

The FA and HA fractions represent 20 to 50% of the DOC of the original samples, depending on the origin, and serve as reference materials. The original aqueous samples and the aqueous solutions of the reference materials were characterized with methods suited for measuring samples at natural concentrations. The DOC normalized values of the spectral absorbances (λ = 254 nm; λ = 436 nm) in the original water samples were highest for the brown water and brown coal water and lowest for the secondary effluents. The FA fractions were similar in the UV-absorbance with the exception of the low-absorbing groundwater FA, reflecting a low density of double bonds. The DOC-normalized proton capacity of the FA fractions (10 to 20 μmol/mg) was highest for the brown coal, brown water, and soil-derived samples and again lowest for the groundwater FA. The high values are due to a higher contribution of the weak acids of phenolic type. Specific data for copper complexation capacity (0.5 to 2.5 μmol/mg) went parallel to the proton capacity. The characterization of the FAs by gel chromatography with organic carbon detection revealed three major fractions. The refractory part at short retention time dominated in the brown water and soil-derived samples, whereas the fractions for the lower molecular mass acids at long retention times were dominant in the secondary effluent and the brown coal isolate. Comparison with UV-detected chromatograms revealed a strong decrease in the specific absorbance of the secondary effluent. Up to 3% of the total mass of the FAs could be identified as hydrolyzable amino acids with the highest yield in the sample from secondary effluent and the lowest one in the groundwater sample. The nitrogen content was always higher in the FAs compared to the HAs of the same origin. The application of gel chromatography fluorescence and fluorescence decay time distribution analysis turned out to be a useful tool to differentiate between the different fractions of NOM, the isolates obtained by different methods (e.g., XAD-8, membrane separation) and the fractions of the samples from different origin and age. This is of special value, for the information can also be obtained for samples with natural NOM concentrations, even though further investigations required for full understanding of the data. This work is part of a multi-disciplinary research program (ROSIG: Refraktäre Organische Säuren in Gewässern), funded by the German Research Association (DFG).     

Removal of NOM in the different stages of the water treatment process

Natural organic matter (NOM) is abundant in natural waters in Finland and in many ways affects the unit operations in water purification. In this study, the organic matter content in water in different stages of a full-scale treatment process over 1 year was measured. The full-scale treatment sequence, studied at the Rusko water treatment plant in Tampere, Finland, consisted of coagulation, flocculation, clarification by sedimentation or flotation, activated carbon (AC) filtration, and disinfection. High-performance size exclusion chromatography (HPSEC) was used for separation to determine changes in the humic substances content during the purification process. In addition, total organic carbon (TOC), KMnO4-number, and UV-absorbance at wavelength 254 nm (UV254) were measured. High molecular weight (HMW) matter was clearly easier to remove in coagulation and clarification than low molecular weight (LMW) matter. Furthermore, depending on the regeneration of the activated carbon filters, activated carbon filtration was effective to a degree but did not remove most of the lowest molecular weight compounds. Significant correlation was established among HPSEC, KMnO4, UV254 absorbance, and TOC. HPSEC proved to be a fast and relatively easy method to estimate NOM content in water and, in fact, gave more information than traditional methods on the type of NOM in a water sample. It also helped the process performance follow-up.     

Phosphate removal by activated carbon–silica nanoparticles composite,kaolin, and olive cake

This work aimed to utilize four low-cost materials, namely activated carbon (AC), activated carbon–nanoparticle composite, kaolin, and olive cake, for phosphate removal. Batch mode tests were used to evaluate the performance of the adsorbents. The parameters affecting the adsorption process such as pH, initial concentration, mixing time, dosage, and temperature were studied. The obtained results showed that the removal efficiency of the adsorbents followed the order of: activated carbon–nanosilica > activated carbon > kaolin > olive cake. The addition of silica nanoparticles significantly enhanced the removal efficiency of activated carbon by 18.1% reaching a removal efficiency of 98% at 15wt% nanosilica loading. The adsorption isotherm data fitted well with Langmuir and Redlich–Peterson models with a correlation coefficient of >0.98, which indicates a monolayer homogenous adsorption. The fitness of the kinetic models was ranked as: pseudo-second-order > pseudo-first-order > intraparticle model. The calculated values of ΔH° = 23.4 kJ/mole, ΔS° = 0.11 kJ/mole, and ΔG = ?7.4 to ?11.8 kJ/mole indicated the endothermic and spontaneous nature of adsorption. The positive value of activation energy (17.66 kJ/mole) and the very low value of the sticking probability (2.4 × 10^?4) suggest high indefinite sticking of the phosphate ions to the adsorbent surface. The removal efficiency increased with time, dosage, and temperature, while it decreased with the increase in the initial concentration at an optimum pH of 7. The obtained results buttressed the benefit of using silica nanoparticles to enhance activated carbon capacity for phosphate removal, while kaolin and olive cake provided lower removal.     

喀斯特地区土壤水中溶解有机碳浓度对植被退化的响应

按退化程度在茂兰喀斯特地区选取的4种不同植被类型依次为原生性乔木森林、次生性乔灌混合林、灌木林、灌丛草坡,并对各植被退化系统中1a内的土壤水中溶解有机碳（DOC）浓度变化特征进行测试分析,并探讨其对不同退化程度的植被的响应特征。结果显示：（1）各种植被类型下土壤水DOC含量按月份均呈现出由低到高、再由高到低的变化趋势,在6月底出现峰值;（2）土壤水DOC含量对降雨量具有很好的响应关系;（3）土壤水DOC含量随植被退化程度的加剧而呈现出递增的趋势,即退化的植被系统中土壤水的DOC含量大于未退化的植被系统,说明未退化的土壤 植被系统比较稳定,不易受到外界因素的干扰,贮存能力大,流失少。研究结果表明对植被退化响应灵敏的土壤水DOC含量可以作为评价土壤和植被关联退化的一个有效指标。     

Correlation of the partitioning of dissolved organic matter fractions with the desorption of Cd,Cu, Ni,Pb and Zn from 18 Dutch soils

Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was also concentrated onto a macroreticular resin and fractionation into three operationally defined fractions: hydrophilic acids (Hyd), humic acids (HA) and fulvic acids (FA). In this manner, change in absolute solution concentration and relative percentage for each fraction could be calculated as a function of extraction equilibrium pH. The soils were also analyzed for solid phase total organic carbon and total recoverable metals (EPA Method 3051). Partitioning coefficients were calculated for the metals and organic carbon (OC) based on solid phase concentrations (less the metal or OC removed by the extraction) divided by solution concentrations. Cu and Pb concentrations in solution as a function of extract equilibrium pH are greatest at low and high pH resulting in parabolic desorption/dissolution curves. While processes such as proton competition and proton promoted dissolution can account for high solution metal concentrations at low pH, these processes cannot account for higher Cu and Pb concentrations at high pH. DOC increases with increasing pH, concurrently with the increase in Cu and Pb solution concentrations. While the absolute concentrations of FA and HA generally increase with increasing pH, the relative proportional increase is greatest for HA . Variation in HA concentrations spans three orders of magnitude while FA concentrations vary an order of magnitude over the pH range examined. Correlation analysis strongly suggests that HA plays a major role in increasing the concentration of solution Cu and Pb with increasing pH in the 18 soils studied. The percentage of the OC that was due to FA was nearly constant over a wide pH range although the FA concentration increased with increasing pH and its concentration was greater than that of the HA fraction at lower pH values (pH = 3-5). Thus, in more acidic environments, FA may play a larger role than HA in governing organo-metallic interactions. For Cd, Ni, and Zn, the desorption/dissolution pattern shows high metal solution concentrations at low pH with slight increases in solution concentrations at extremely high pH values (pH>10). The results presented here suggest that the effects of dissolved organic carbon on the mobilization of Cd, Ni, and Zn may only occur in systems governed by very high pH. At high pH, it is difficult to distinguish in this study whether the slightly increased solution-phase concentrations of these cations is due to DOC or hydrolysis reactions. These high pH environments would rarely occur in natural settings.     

Pre-assessment of the speciation of 60Co, 125Sb, 137Cs and 241Am in a contaminated aquifer

A sample of contaminated groundwater was analyzed using a combination of wet techniques to obtain geochemical information on the mobile species of 60Co, 125Sb, 137Cs and 241Am. The techniques were combined in a scheme to determine the predominant character of the radionuclides in negative or positive fractions, size separation by ultrafiltration, and their association with natural organic matter (NOM). The analyses indicated that the radionuclides of interest were predominantly in the negative fraction. Most of the 60Co and 125Sb were in the small size fraction (<5000 Da), and 137Cs and 241Am were found with the larger, colloidal-sized material. Antimony-125 and 60Co were predominantly in the hydrophilic fraction, while 137Cs and 241Am were found in hydrophobic fractions. Our analysis indicated that 137Cs is found in the same fraction as the large-sized colloidal (hydrophobic) material, suggesting an association with NOM. The results suggested that 60Co and 241Am were associated with NOM, in different size fractions, suggesting that these two nuclides are bound to different sites. Finally, the 125Sb results were inconclusive, whether this nuclide is associated with NOM, or it is inorganic.     

Removal of copper from water using limestone filtration technique. Determination of mechanism of removal

This paper discusses heavy metal removal from wastewater by batch study and filtration technique through low-cost coarse media. Batch study has indicated that more than 90% copper (Cu) with concentration up to 50 mg/l could be removed from the solution with limestone quantity above 20 ml (equivalent to 56 g), which indicates the importance of limestone media in the removal process. This indicates that the removal of Cu is influenced by the media and not solely by the pH. Batch experiments using limestone and activated carbon indicate that both limestone and activated carbon had similar metal-removal efficiency (about 95%). Results of the laboratory-scale filtration technique using limestone particles indicated that above 90% removal of Cu was achieved at retention time of 2.31 h, surface-loading rate of 4.07 m3/m2 per day and Cu loading of 0.02 kg/m3 per day. Analyses of the limestone media after filtration indicated that adsorption and absorption processes were among the mechanisms involved in the removal processes. This study indicated that limestone can be used as an alternative to replace activated carbon.     

Characterization of Norwegian natural organic matter: Size,diffusion coefficients,and electrophoretic mobilities

Eighteen Norwegian NOM samples were analyzed by AFM, TEM, FCS, and CE. The TEM and AFM gave complementary, but not identical, information regarding the conformation of the NOM. A large majority of the material in all samples appeared as points with a size of approximately 2 nm or less. FCS gave values for diffusion coefficients which were in the range 2.1–3.0 × 10⁻¹⁰ m² s⁻¹. This corresponds to molecular diameters of between 1.6 and 2.0 nm, in reasonable agreement with both TEM and AFM. Electropherograms, using absorbance at 200 nm, were all dissimilar except for the Gjerstad and Hellerudmyra sample pairs, for which no major differences were observed. CE was also carried out using both fluorescence (excitation at 325, 457, and 488 nm) and UV-absorbance (200, 210, 254, and 288 nm) detection on three of the NOM samples. The different modes of detection and wavelengths gave qualitatively similar electropherograms. Calculated EPMs of the major sample components were in the range -2.0 to -5.0 10⁻⁸ m² s⁻¹ V⁻¹.     

Comparison of distribution coefficients for americium and curium: Effects of pH and naturally occurring colloids

Distribution coefficients (K_D) were measured by a batch technique for sorption of americium-243 and curium-244 to Lake Michigan sediment from four different natural surface waters. The dependences of K_D values on pH and on the concentrations of naturally occurring colloidal organic carbon (COC) were studied. The comparison of K_D values showed that, while changes in pH and in COC concentrations cause significant changes in sorption for both americium and curium, neither variable causes a significant difference in sorption between these two elements.     

Fluorescence analysis for multi-site aluminum binding to natural organic matter

Natural organic matter (NOM) samples isolated from different water sources in Norway were compared using their fluorescence properties. Fluorescence surfaces were observed at pH 4.36 and deconvoluted using SIMPLISMA (Windig and Guilment 1991). There were a total of seven different fluorophores observed for these samples and each sampling site had between four and six of the fluorescent components. These components were observed to bind Al during titrations at the same pH. Multiresponse titration curves were fit using the method of Smith and Kramer (1998) and most of the binding strengths are similar to values for Suwannee River fulvic acid (logK' between 4.8 and 5.5), but there are strong sites (logK' = 7) and weak sites (logK' between 3 and 4) also observed. Results depended on the isolation method used; reverse osmosis and low pressure evaporation yielded different values but with no consistent trends.     

Biological vs. chemical properties of natural organic matter isolated from selected Norwegian lakes

Relationships among different spectroscopic, chemical, and biological properties of dissolved natural organic matter (NOM) were investigated. NOM samples were isolated by means of reverse osmosis from eight Norwegian lakes. Elemental composition, absorption spectra (UV, VIS, IR), the influence on algal growth, and accumulation rates of metals by mussels in the presence of NOM were measured. Linear regression and principal components analyses were utilised to assess relationships between the biological and chemical properties. It was concluded that the content of organic matter in the isolates and the aromaticity of NOM, as characterised by UV and VIS spectra, are best correlated with the biological properties.     

Can current management maintain forest landscape multifunctionality in the Eastern Alps in Austria under climate change?

In Central Europe, management of forests for multiple ecosystem services (ES) has a long tradition and is currently drawing much attention due to increasing interest in non-timber services. In face of a changing climate and diverse ES portfolios, a key issue for forest managers is to assess vulnerability of ES provisioning. In a case study catchment of 250 ha in the Eastern Alps, the currently practiced uneven-aged management regime (BAU; business as usual) which is based on irregularly shaped patch cuts along skyline corridors was analysed under historic climate (represented by the period 1961–1990) and five transient climate change scenarios (period 2010–2110) and compared to an unmanaged scenario (NOM). The study addressed (1) the future provisioning of timber, carbon sequestration, protection against gravitational hazards, and nature conservation values under BAU management, (2) the effect of spatial scale (1, 5, 10 ha grain size) in mapping ES indicators and (3) how the spatial scale of ES assessment affects the simultaneous provision of several ES (i.e. multifunctionality). The analysis employed the PICUS forest simulation model in combination with novel landscape assessment tools. In BAU management, timber harvests were smaller than periodic increments. The resulting increase in standing stock benefitted carbon sequestration. In four out of five climate change scenarios, volume increment was increasing. With the exception of the mildest climate change scenario (+2.6 °C, no change in precipitation), all other analysed climate change scenarios reduced standing tree volume, carbon pools and number of large old trees, and increased standing deadwood volume due to an intensifying bark beetle disturbance regime. However, increases in deadwood and patchy canopy openings benefitted bird habitat quality. Under historic climate, the NOM regime showed better performance in all non-timber ES. Under climate change conditions, the damages from bark beetle disturbances increased more in NOM compared with BAU. Despite favourable temperature conditions in climate change scenarios, the share of admixed broadleaved species was not increasing in BAU management, mainly due to the heavy browsing pressure by ungulates. In NOM, it even decreased and mean tree age increased. Thus, in the long run NOM may enter a phase of lower resilience compared with BAU. Most ES indicators were fairly insensitive to the spatial scale of indicator mapping. ES indicators that were based on sparse tree and stand attributes such as rare admixed tree species, large snags and live trees achieved better results when mapped at larger scales. The share of landscape area with simultaneous provisioning of ES at reasonable performance levels (i.e. multifunctionality) decreased with increasing number of considered ES, while it increased with increasing spatial scale of the assessment. In the case study, landscape between 53 and 100 % was classified as multifunctional, depending on number and combinations of ES.     

Combating dye pollution using cocoa pod husks: a sustainable approach

The adsorptive potential of activated carbon prepared by chemical activation of Cocoa pod husk (CPHAA) to remove Congo red (CR) dye from its aqueous solution was investigated in this study. CPHAA was characterised using Energy Dispersive X-Ray, Scanning Electron Micrograph and Fourier Transform Infrared Spectroscopy techniques. The effects of contact time, initial dye concentration, pH and solution temperature were studied. Equilibrium data were fitted to Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The equilibrium data were best represented by Langmuir isotherm model, with maximum monolayer adsorption capacity of 43.67 mg/g. The kinetic data were fitted to Pseudo-first-order, Pseudo-second-order, Elovich and Intraparticle diffusion models; the pseudo-second-order kinetic model provided the best correlation. Thermodynamic parameters such as standard enthalpy (ΔH^o), standard entropy (ΔS^o) and standard free energy (ΔG^o) were evaluated. The thermodynamic study showed that the process is endothermic, spontaneous and feasible. The mean free energy of adsorption shows that the mechanism is by physisorption. CPHAA was found to be an effective adsorbent for the removal of CR dye from aqueous solution.