Frequency analysis of annual maximum suspended sediment concentrations in Abiod wadi,Biskra (Algeria)

Sediment transport processes in the Mediterranean semi‐arid areas have interested a great number of hydrologists and statisticians. Frequency analysis (FA) procedures are commonly applied for several hydrological events such as floods and droughts. However, in general, FA is not widely applied to treat suspended sediment concentration (SSC), especially in semi‐arid regions. In the present study, an FA was performed on SSC data from 1979 to 1991 observed upstream from the Foum El Gherza dam, which is located at Biskra in the South–East of Algeria. This dam is problematic in terms of silting. Therefore, this study is mainly motivated by providing an FA model and risk evaluation in order to assist dam managers to better evaluate the potential of silting resulting from SSC transport to the reservoir. Probability distributions commonly used in hydrology were tested to SSC data recorded at the M'chounech station on Abiod wadi located upstream the dam. All the FA steps were considered; including classical techniques (e.g. goodness‐of‐fit tests, statistical criteria) as well as recently developed tools (tail distribution classification). Their application led to the selection of the lognormal distribution (LN2) to fit the considered data, and hence an accurate risk assessment could be obtained. Because of the presence of a slight trend, non‐stationary models are also considered in the present study. Copyright © 2013 John Wiley & Sons, Ltd.     

Blanket peat erosion and sediment yield in an upland reservoir catchment in the southern Pennines,UK

This paper investigates temporal variations in fluxes of peat and other sediment in the catchment of March Haigh Reservoir, West Yorkshire. Long‐term estimates of sediment yield were derived from a study of reservoir sediments. Magnetic properties were used to correlate ten cores to a master profile dated using ²¹⁰Pb and ¹³⁷Cs. A ¹⁴C date suggests that most of the organic component of the sediment is allochthonous and derived from peat eroded from the catchment. Organic sediment yields suggest low catchment erosion rates between 1838 and 1963. Blanket peat erosion increased significantly after 1963, and peaked between 1976 and 1984. Estimates of total sediment yield range between 2 and 28 t km^?2 a^?1. These yields are significantly lower than those from some previous studies examining reservoir sedimentation in other blanket peat‐covered catchments. The low yield estimates may be due to relatively low rates of erosion in the basin, but may also be partly explained by maintenance of silt traps during the early life of the reservoir and removal of sediment by scouring. Sedimentation within the reservoir is spatially variable, and bathymetry and sediment source appear to be the dominant controls on sedimentation patterns within the reservoir. Copyright © 2005 John Wiley & Sons, Ltd.     

Estimating the sediment trap efficiency of intermittently dry reservoirs: lessons from the Kruger National Park,South Africa

The assessment of sediment yield from reservoir siltation requires knowledge of the reservoir's sediment trap efficiency (TE). Widely used approaches for the estimation of the long‐term mean TE rely on the ratio of the reservoir's storage capacity (C) to its catchment size (A) or mean annual inflow (I). These approaches have been developed from a limited number of reservoirs (N ≤ 40), most of them located in temperate climate regions. Their general applicability to reservoirs receiving highly variable runoff such as in semi‐arid areas has been questioned. Here, we examine the effect of ephemeral inflow on the TE of 10 small (≤ 280 × 10³ m³), intermittently dry reservoirs located in the Kruger National Park. Fieldwork was conducted to determine the storage capacity of the reservoir basins. The frequency and magnitude of spillage events was simulated with the daily time step Pitman rainfall–runoff model. Different runoff scenarios were established to cope with uncertainties arising from the lack of runoff records and imperfect input data. Scenarios for the relationship between water and sediment discharge were created based on sediment rating curves. Taking into account uncertainties in hydrological modelling, uncertainties of mean TE estimates, calculated from all scenarios (N = 9), are moderate, ranging from ±6 to ±11% at the 95% confidence level. By comparison, estimating TE from the storage capacity to catchment area (C/A) ratio induces high uncertainty (ranges of 35 to 65%), but this uncertainty can be confined (15 to 33%) when the latter approach is combined with hydrological modelling. Established methods relying on the storage capacity to mean annual inflow (C/I) ratio most probably lead to an overestimation of the TE for the investigated reservoirs. The approach presented here may be used instead to estimate the TE of small, intermittently dry reservoirs in semi‐arid climate regions. Copyright © 2017 John Wiley & Sons, Ltd.     

Composition and mass flux of sediment entering the world's subduction zones: Implications for global sediment budgets, great earthquakes, and volcanism

Lithologic data compiled from Deep Sea Drilling Project and Ocean Drilling Program sites, when combined with orthogonal convergence rates at convergent plate boundaries, permit quantification of the mass flux of sediment into subduction zones. We have made such calculations for each major sediment component — terrigenous grains, calcium carbonate, opal, and water — for twelve trench systems. Results show that 1.4 × 10¹⁵ g/yr of sediment and 0.9 × 10¹⁵ g/yr of water enter the trenches in the oceanic sedimentary layer. Most of the entering sediment, 1.1 × 10¹⁵ g/yr, is terrigenous; the remainder is more carbonate than opal. For most of geologic time an order of magnitude more sediment enters the ocean than leaves it via subduction. The global sedimentary cycle need be in balance only over an entire Wilson cycle. Comparison of sediment fluxes into trenches with the magnitude of large earthquakes and with the composition of bulk volcanic rock shows no correlation.     

Reservoir siltation in the semi‐arid highlands of northern Ethiopia: sediment yield–catchment area relationship and a semi‐quantitative approach for predicting sediment yield

Due to shortage of rainfall and its increasing variability, moisture stress is identified to be one of the most critical factors affecting agricultural productivity in the drylands of Ethiopia. To circumvent this problem, a strategy of supplemental irrigation through surface water harvesting was adopted by the government and several micro‐dams have been built in the semi‐arid parts of the country. However, the benefits from the water harvesting schemes are not sustainable because of rapid water storage loss due to siltation. There is, therefore, an urgent need for improved catchment‐based erosion control and sediment management strategies. The design and implementation of such strategies require data on the rate and magnitude of sediment deposition. To this end, reservoir surveys were conducted to estimate sediment deposition rate for 11 reservoirs identified to be representative of catchments in the Tigray region of northern Ethiopia. Two approaches were employed during the survey: one was based on measurement of sediment thickness in reservoirs while the other was based on comparing the original and existing topography of the reservoir‐beds. The average annual sediment yield estimated for the study sites was about 19 t ha^?1 y^?1. An equation of the type SSY = 3á36A^0á67 (with SSY = area specific sediment yield in t ha^?1 y^?1 and A = catchment area in km²) was also established for the study region, which is opposite to the ‘universal’ SSY–A relationship. In order to improve the sediment yield predictive capability of A, it was integrated with a factorial index that assesses the catchment's propensity to erosion and potential sediment yield. The effect of accelerated sediment deposition on water storage loss of reservoirs and possible controlling factors of the SSY–A relationship are outlined. The potential semi‐quantitative scoring approach to characterize catchments in terms of erosion sensitivity and the significance of the A‐index approach to predict SSY of similar catchments are also highlighted. Copyright © 2006 John Wiley & Sons, Ltd.     

Application of ~(137)Cs fingerprinting technique to interpreting sediment production records from reservoir deposits in a small catchment of the Hilly Loess Plateau, China

According to variations of 137Cs and clay contents, 44 flood couplets were identified in a profile of res- ervoir deposit with a vertical length of 28.12 m in the Yuntaishan Gully. Couplet 27 at the middle of the profile had the highest average 137Cs content of 12.65 Bq·kg?1, which indicated the 1963s' deposits, then 137Cs content decreased both downward and upward in the profile. The second top and bottom couplets had average 137Cs contents of 2.15 Bq·kg?1 and 0.92 Bq·kg?1, respectively. By integrated analysis of reservoir construction and management history, variations of 137Cs contents over the profile, sediment yields of flood couplets and rainfall data during the period of 1958-1970, individual storms related to the flood couplets were identified. 44 floods with a total sediment yield of 2.36×104 m3 occurred and flood events in a year varied between 1 and 10 times during the period of 1960-1970. 7-10 flood events occurred during the wet period of 1961-1964 with very wet autumn, while only 1-2 events during the dry period of 1965-1969. Average annual specific sediment yield was 1.29×104 t·km?2·a?1 for the Yuntaishan Gully during the period of 1960-1970, which was slightly higher than 1.11 ×104 t·km?2·a?1 for the Upper Yanhe River Basin above the Ganguyi Hydrological Station and slightly lower than 1.40 ×104 t·km?2·a?1 for the nearby Zhifang Gully during the same period. Annual specific sediment yields for the Yuntaishan Gully were correlated to the wet season's rainfalls well.     

InSAR analysis of a blind thrust rupture and related active folding: the 1999 Ain Temouchent earthquake (M w 5.7, Algeria) case study

We study the surface deformation associated with the 22 December 1999 earthquake, a moderate sized but damaging event at Ain Temouchent (northwestern Algeria) using Interferometric Satellite Aperture Radar images (InSAR). The mainshock focal mechanism solution indicates reverse faulting with a NE–SW trending rupture comparable to other major seismic events of this section of the Africa–Eurasia plate boundary. Previously, the earthquake fault parameters were, however, poorly known because no aftershocks were precisely determined and no coseismic surface ruptures were observed in the field. Using a pair of ERS data with small baseline and short temporal separation in the ascending orbit we obtained an interferogram that shows the coseismic surface displacement field despite poor coherence. The interferogram measures four fringes and displays an ellipse-shaped lobe with ∼11 cm peak line-of-sight displacement. The elastic modeling using a boundary element method (Poly3Dinv) indicate coseismic slip reaching up to 1 m at 5 km depth on the N 57° E trending, dipping 32° NW Tafna thrust fault. The geodetic estimate of seismic moment is 4.7 × 10¹⁷ N m. (Mw 5.7) in is good agreement with seismological results. The elliptical shape of the surface displacement field coincides with the NE–SW trending Berdani fault-related fold. The consistency between the geological observations and InSAR solution shed light on the precise earthquake location and related Tafna fault parameters.     

Evidence for Quaternary liquefaction-induced features in the epicentral area of the 21 May 2003 Zemmouri earthquake (Algeria, M w = 6.8)

Evidence of ancient liquefaction-in duced features is presented in the area of the 2003 Zemmouri earthquake (M _w 6.8). This earthquake was related to an offshore unknown 50-km long fault. A 0.55-m coseismic coastal uplift was generated and extensive liquefaction has been induced in the most susceptible area which correspond to the seaside and along the hydrographic network, mainly the Sebaou and Isser valley rivers. Field investigations allowed us to identify past liquefaction traces in the Quaternary deposits. The observed features are represented by sand dikes, sills, and sand vents as well as well-preserved sand boiled volcanoes. In this work, we also describe the alluvial environment, the hosted localized stratigraphic layer, the morphology and the geometry of the observed features, as well as the observed deformation (settlement) of the hosted layers that are among characteristics of the seismically induced features as described in worldwide examples. Our observations represent a step towards paleoseismological studies in the region knowing that the May 21st 2003 Zemmouri earthquake is produced by an offshore fault where a direct study of the seismogenic fault is inaccessible.     

Water and sediment balances of a contour bench terracing system in a semi-arid cultivated zone (El Gouazine,central Tunisia)

Abstract

Contour benches are earthen structures constructed across cultivated slopes, at intervals down the slope, largely used in semi-arid zones. The results of an experiment to monitor water and sediment balance inside a contour bench terrace system are presented. The study site, located in the El-Gouazine watershed (central Tunisia), includes two terraced plots of approximately 3000 m², one of which was left fallow for several years, while the other was tilled. The characteristics of rainfall—runoff processes and erosion inside both terraced plots during a two-year period (2004–2006) are described. Ploughing reduced runoff by 75%. Erosion was monitored following runoff episodes that produced observable deposits in the bench channel. After ploughing, erosion was reduced by 44% between July 2004 and July 2005 and by 50% between October 2005 and July 2006. However, erosion per millimetre of runoff was about twice as great on the tilled soil as on the fallow. Even though ploughing weakens the soil, it seems to reduce erosion by increasing infiltration. For the studied rain events, ploughing used in combination with contour bench terraces seems to have limited erosion and enhanced the effectiveness of contour bench terrace management.     

Bioremediation of contaminated coastal sediment: Optimization of slow release biostimulant ball using response surface methodology (RSM) and stabilization of metals from contaminated sediment

The aim of the present study is to optimize the slow release biostimulant ball (BSB) for bioremediation of contaminated coastal sediment using response surface methodology (RSM). Metals contamination and stabilization of metals in coastal sediments using BSB were investigated. The effects of BSB size (1–5 cm), distance (1–10 cm), and time (1–4 months) on the stabilization of metals including Fe, Cd, Cu, and Pb were determined. The maximum stabilization percentages of Fe, Cd, Cu, and Pb, of 64.5%, 54.9%, 63.8%, and 47.6%, respectively, were observed at a 3 cm ball size, 5.5 cm distance, and a period of 4 months; these values are the optimum conditions for effective treatment of contaminated coastal sediment. The determination coefficient of the R² value suggests that > 91.55%, 89.97%, 96.10%, and 86.40% of the variance is attributable to the variables of Fe, Cd, Cu, and Pb, respectively.     

Land use changes,torrent control works and sediment mining: effects on channel morphology and sediment flux,case study of the Reno River (Northern Italy)

As with most Italian rivers, the Reno River has a long history of human modification, related also to morphological changes of the lower Po River since Roman times, but in the last decades, significant land use changes in the headwaters, dam construction, torrent control works and extensive bed material mining have caused important channel morphology and sediment budget changes. In this paper, two main types of channel adjustment, riverbed incision and channel narrowing, are analysed. Riverbed degradation is discussed by comparing four different longitudinal profiles surveyed in 1928, 1951, 1970 and 1998 in the 120 km long reach upstream of the outlet. The analysis of channel narrowing is carried out by comparing a number of cross‐sections surveyed in different years across the same downstream reach. Field sediment transport measurements of seven major floods that occurred between 2003 and 2006 are compared with the bedload transport rates predicted by the most renowned equations. The current low bedload yield is discussed in terms of sediment supply limited conditions due to land use changes, erosion‐control works and extensive and out of control bed material mining that have affected the Reno during the last decades. Copyright © 2011 John Wiley & Sons, Ltd.     

The Boumerdes (Algeria) earthquake of May 21, 2003 (<Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript> = 6.8): Ground deformation and intensity

A destructive earthquake of magnitude M_w = 6.8 hit the region of Boumerdes and Algiers (Algeria) on May 21, 2003. This is among the strongest seismic events of the mediterranean region and the most important event in the capital Algiers since 1716. It caused a widespread damage in the epicentral region, claimed 2271 human lives, injured 10000, about 20000 housing units affected and left about 160000 homeless. The main shock was felt about 250 km far from the epicenter and triggered sea waves of 1–3 m in amplitude in Balearic islands (Spain). Based on field observations and press report an intensity IX (MSK scale) is attributed to the epicentral area. The main shock was followed by many aftershocks among them several are of magnitude greater than 5.0, which added panic to inhabitants. The main shock triggered ground deformation, particularly liquefaction whose features are in different forms and sizes and caused damage and collapse of roads. The focal mechanism determined by worldwide institutions yield a pure reverse faulting with a compressional axis striking NE-SW. The epicenter is located offshore about 7 km from the Boumerdes-Dellys coast. Field observations show 0.7 m of coseismic uplift of shoreline between Boudouaou and Dellys. This uplift is about a half of the extracted coseismic slip from the seismic moment. On the other hand there is no clear surface break onshore, confirming hence, that the causative active fault is offshore. However, the rupture may propagate onshore to the SE near the Boudouaou region where ground cracks showing reverse faulting are observed a long a corridor of about 1 km wide. These fissures may correspond to a diffuse coseismic deformation.     

Evidence for fault-related directionality and localized site effects from strong motion recordings of the 2003 Boumerdes (Algeria) earthquake: Consequences on damage distribution and the Algerian seismic code

The Algiers–Boumerdes region has been struck by a destructive magnitude 6.8 (M_w) earthquake on May 21, 2003. The study presented in this paper is based on main shock strong motions from 13 stations of the Algerian accelerograph network. A maximum 0.58g peak ground acceleration (PGA) has been recorded at 20 km from the epicenter, only about 150 m away from a PGA of 0.34g, with both a central frequency around 5 Hz, explained by a strong very localized site effect, confirmed by receiver function technique results showing peaks at 5 Hz with amplitudes changing by a factor of 2. Soil amplifications are also evidenced at stations located in the quaternary Mitidja basin, explaining the higher PGA values recorded at these stations than at stations located on firm soil at similar distances from the epicenter. A fault-related directionality effect observed on the strong motion records and confirmed by the study of the seismic movement anisotropy, in agreement with the N65 fault plan direction, explains the SW–NE orientation of the main damage zone. In the near field, strong motions present a high-frequency content starting at 3 Hz with a central frequency around 8 Hz, while in the far field their central frequency is around 3 Hz, explaining the high level of damage in the 3- to 4-story buildings in the epicentral zone. The design spectra overestimate the recorded mean response spectra, and its high corner frequency is less than the recorded one, leading to a re-examination of the seismic design code that should definitively integrate site-related coefficient, to account for the up to now neglected site amplification, as well as a re-modeling of the actual design spectra. Finally, both the proposed Algerian attenuation law and the worldwide laws usually used in Algeria underestimate the recorded accelerations of the 6.8 (M_w) Boumerdes earthquake, clearly showing that it is not possible to extrapolate the proposed Algerian law to major earthquakes.     

Variable water‐saturated areas and streamflow generation in the small Ringelbach catchment (Vosges Mountains,France): the master recession curve as an equilibrium curve for interactions between atmosphere,surface and ground waters

In the small Ringelbach research catchment, where studies on the water cycle components in a granitic mountainous environment have been conducted since 1976, the water‐saturated areas that are hydraulically connected to the outlet play a major role in the streamflow generation, as it is here that complex interactions between atmosphere, surface and ground waters take place. During baseflow recession periods, which may last several months between two groundwater recharge events, the atmospheric inputs of water and energy on these contributing areas only explain the streamflow fluctuations observed around the master recession curve, which defines the groundwater contribution: fluctuating above it in the case of precipitation input on these areas, below it in the case of evaporation output from these areas. Streamflow may therefore largely deviate from the master recession curve in the case of long, hot, dry spells. Detailed mapping has shown that their variable extent is well related to baseflow by a loglinear curve. On the other hand, a synthetic master recession curve, well fitted by a second‐order hyperbolic function, has been obtained from numerous pure recession periods. Both based on these two curves, a simple procedure and a simple model have been used to (i) validate the hypothesis that the connected saturated areas are the only permanent variable contributing areas and (ii) simulate the daily streamflow volumes over long baseflow recession periods by a water balance of the aquifer below these areas only. The storm runoff ratio for small to moderate rainfall events is indeed corresponding to the catchment saturated fraction at that time. The volume of daily streamflow oscillations is indeed corresponding to the evaporation at the potential rate from the saturated areas only. In both cases, streamflow naturally tends towards the master recession curve after the end of any atmospheric perturbation. Introducing these findings into TOPMODEL led to significantly improved simulation results during baseflow recession periods. The master recession curve may therefore be considered as a dynamic equilibrium curve. Together with the relationship between saturated extent and baseflow, it provides the main characteristics necessary to understand and model the interactions at this complex interface and the resulting daily streamflow variations during baseflow recession periods in this type of catchment. Copyright © 2016 John Wiley & Sons, Ltd.     

Stereophotogrammetry of archive data and topographic approaches to debris‐flow torrent measurements: calculation of channel‐sediment states and a partial sediment budget for Manival torrent (Isère,France)

This paper focuses on a topographic methodology to characterize the amount of sediment stored in channels and the use of historical photographs for aerial survey by stereophotogrammetry, as part of wider research on debris‐flow magnitude prediction. The topographic methodology uses equidistant four‐point cross‐sections along the long profile of the channel. Each cross‐section is representative of a 50‐m reach of the channel. To calculate the volume of each reach, the difference is calculated between a reference level and the topographic surface. The reference level is the lowest level where the debris flow can erode, and in the current method this level is estimated from fixed points along the long profile of the channel. The accuracy of the method has been estimated by comparing results of a detailed topographic survey, with a standard deviation corresponding to about 6 per cent of the total calculated sediment volume. This topographic methodology has been used on aerial photographs by photogrammetry. This tool was applied to photographs taken on 12 past dates. The scales of the archive photographs used range from 1:3000 to 1:30 000, but results are consistent and permit us to calculate sediment states of the channel for different past dates with an uncertainty of about 6 per cent of the total volume. The application of the technique to the Manival debris‐flow torrent has permitted us to propose some partial sediment budgets and erosion‐rate estimates. Copyright © 2006 John Wiley & Sons, Ltd.     

Recent changes in the sediment regime of the Pearl River (South China): Causes and implications for the Pearl River Delta

Riverine sediments have played an important role in the morphological evolution of river channels and river deltas. However, the sediment regime in the many world's rivers has been altered in the context of global changes. In this study, temporal changes in the sediment regime of the Pearl River were examined at different time scales, that is, annual, seasonal, and monthly time scales, using the Mann–Kendall test. The results revealed that precipitation variability was responsible for monthly and seasonal distribution patterns of the sediment regime and the long‐term changes in the water discharge; however, dam operation has smoothed the seasonal distribution of water discharge and resulted in decreasing trends in the annual, wet‐season, and dry‐season sediment load series since the 1950s. Due to the different regulation magnitudes of dam operation, differences were observed in sediment regime changes among the three tributaries. In addition, human activities have altered the hysteresis of seasonal rating curves and affected hysteresis differences between increasing and decreasing water discharge stages. Sediment supply is an important factor controlling river channel dynamics, affecting channel morphology. From the 1950s to the 1980s, siltation was dominant in river channels across the West River and North River deltas in response to the sediment increases; however, scouring occurred in the East River deltas due to sediment reduction. Significant erosion occurred in river channels in the 1990s, which was mostly due to downcutting of the river bed caused by sand excavations and partly because of the reduced sediment load from upstream. Although sand excavations have been banned and controlled by authority agencies since 2000, the erosion of cross sections was still observed in the 2000s because of reduced sediment caused by dam construction. Our study examines the different effects of human activities on the sediment regime and downstream channel morphology, which is of substantial scientific importance for river management.     

A methodology for historical assessment of compliance with environmental water allocations: lessons from the Crocodile (East) River,South Africa

Abstract

Environmental flow provisions are a legal obligation under South Africa’s National Water Act (1998) where they are known as the “ecological reserve”, which is now being realized in river operations. This article presents a semi-quantitative method, based on flow–duration curve (FDC) analysis, used to assess the compliance of the Crocodile (East) River with the reserve in an historical context. Using both monthly and daily average flow data, we determine the extent and magnitude of non-compliant flows against environmental water requirements (EWRs) for three periods (1960–1983, 1983–2000, and 2000–2010). The results suggest a high degree of non-compliance, with the reserve increasing with each of these periods (14%, 35%, and 39% of the time), respectively, where effects were most pronounced in the low-flow season. The results also suggest that, whilst the magnitudes of reserve infringements for the latter period are relatively high, there appears to have been some improvement since the implementation of the river’s operating rules.

Editor Z.W. Kundzewicz; Guest editor M. Acreman

Citation Riddell, E., Pollard, S., Mallory, S., and Sawunyama, T., 2014. A methodology for historical assessment of compliance with environmental water allocations: lessons from the Crocodile (East) River, South Africa. Hydrological Sciences Journal, 59 (3–4), 831–843.     

Cercis siliquastrum Tree Leaves as an Efficient Adsorbent for Removal of Ag(I): Response Surface Optimization and Characterization of Biosorption

The Cercis siliquastrum tree leaves are introduced as a low cost biosorbent for removal of Ag(I) from aqueous solution in a batch system. FT‐IR, XRD analysis, and potentiometric titration illustrate that the adsorption took place and the acidic functional group (carboxyl) of the sorbent was involved in the biosorption process. In addition, it was observed that the pH beyond pH_pzc 4.4 is favorable for the removal procedure. The effect of operating variables such as initial pH, temperature, initial metal ion concentration, and sorbent mass on the Ag(I) biosorption was analyzed using response surface methodology (RSM). The proposed quadratic model resulting from the central composite design approach (CCD) fitted very well to the experimental data. The optimum condition obtained with RSM was an initial concentration of Ag(I) of 85 mg L^?1, pH = 6.3 and sorbent mass 0.19 g. The applicability of different kinetic and isotherm models for current biosorption process was evaluated. The isotherm, kinetic, and thermodynamic studies showed the details of sorbate‐sorbent behavior. The competitive effect of alkaline and alkaline earth metal ions during the loading of Ag(I) was also considered.     

Base Treated Cogon Grass (Imperata cylindrica) as an Adsorbent for the Removal of Ni(II): Kinetic,Isothermal and Fixed‐bed Column Studies

The adsorption of Ni(II) from aqueous solutions using base treated cogon grass or Imperata cylindrica (NHIC) was performed under batch and column modes. Batch experiments were conducted to determine the factors affecting adsorption such as pH, adsorbent dosage, initial nickel concentration, contact time and temperature. The fixed‐bed column experiment was performed to determine the practical applicability of NHIC and to obtain the breakthrough curve. Adsorption was fast as equilibrium was achieved within 60 min, and was best described by the pseudo second order model. According to the Langmuir model, a maximum adsorption capacity of 6.96 mg/g was observed at pH 5 and at a temperature of 313 K. Thermodynamic parameters such as ΔG⁰, ΔH⁰ and ΔS⁰ were calculated, and indicated that adsorption was a spontaneous and endothermic process. The mechanistic pathway of Ni(II) uptake was examined by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) spectroscopy. The Thomas and Yoon‐Nelson models were used to analyze the fixed‐bed column data.