PO 4 3? Removal by and Permeability of Industrial Byproducts and Minerals: Granulated Blast Furnace Slag, Cement Kiln Dust, Coconut Shell Activated Carbon, Silica Sand, and Zeolite

Excess PO ₄ ^3? from agricultural subsurface drainage and runoff degrades the overall water quality of the receiving surface waters in a cumulatively damaging process known as eutrophication. In the past 25 years, PO ₄ ^3? removal by industrial byproducts and minerals has received considerable attention because these materials are both abundant and inexpensive. In this study, the saturated falling-head hydraulic conductivity and phosphate removal capability of granulated blast furnace slag (GBFS), cement kiln dust (CKD), zeolite, silica sand, and coconut shell activated carbon (CS-AC) were assessed. GBFS, zeolite, silica sand, CS-AC, and 5:95% and 10:90% CKD/sand blends all exhibited hydraulic conductivities ??0.001 cm/s. GBFS and the CKD/sand blends exhibited >98% PO ₄ ^3? removal while CS-AC removed 70?C79% of initial PO ₄ ^3? concentrations. In contrast, silica sand and zeolite removed 21?C58% of PO ₄ ^3? . The phosphate removal data for each material was modeled against the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Frumkin sorption isotherms to yield insight into possible removal mechanisms. Overall, GBFS, CKD, zeolite, silica sand, and CS-AC were sufficiently permeable and removed significant amounts of PO ₄ ^3? and should be considered for use in treatment of agricultural effluent.     

Reactions of zinc with iron-oxide coated calcite surfaces at alkaline pH

Both iron oxides and carbonate minerals, such as calcite, can sorb zinc (Zn), and therefore are important in controlling the solution concentration and availability of Zn to plants growing in calcareous soil. When present together, interactions between these components affect their sorption behaviour. We investigated changes in the reactions of Zn with calcite at alkaline pH, as the calcite surface was progressively coated by iron oxide. Coated calcite surfaces were prepared that had from 0.05 to 1.45% iron oxide. The initial concentration of Zn and the amount of iron oxide on the calcite were the most critical factors affecting adsorption, precipitation of solid phases, and the desorbability of sorbed Zn. For pure calcite at small initial Zn concentrations (< 2.5 × 10^?5 m ) adsorption was dominant; with increasing concentration, precipitation of hydrozincite (ZHC) became more important. With increasing amounts of iron oxide the amount of Zn adsorbed increased, the desorbability of the Zn decreased, and precipitation became progressively less evident, and at 1.45% iron oxide content there was no evidence of any precipitation of ZHC. The calculated maximum adsorption attributable to the iron oxide coating was inversely proportional to the thickness of the oxides on the calcite, and greatly exceeded that of iron oxide as a separate phase. The common occurrence of iron‐coated carbonates in calcareous soils and their capacity to adsorb Zn contributes to the problems of Zn deficiency, for which these soils are noted.     

Laboratory Study of Stormwater Biofiltration in Low Temperatures: Total and Dissolved Metal Removals and Fates

Stormwater biofilters, which are recommended for application in both Water-Sensitive Urban Design and Low Impact Development, can remove up to 80% or 90% of total metals found in stormwater. However, their winter operation is a common concern. That was addressed in this study by investigating the metal removal effectiveness of replicate laboratory biofilter mesocosms at 2°C, 8°C and 20°C. As recommended for cold climate bioretention, coarse filter media were implemented and in the top 100 mm layer topsoil was added to increase the sorption capacity. Cd, Cu, Pb and Zn concentrations measured in the biofilter effluent were far below those in the influent and this significantly improved the treated stormwater quality. Contrary to a common notion that coarse media in the main filter body impair dissolved metal sorption, satisfactory removals of dissolved metals were found in this study with most metal burdens retained in the top layer of the filter in which the sorption capacity was enhanced by topsoil. Some metal uptake by the plants was also detected. Temperature did not affect Cd, Pb and Zn removals in general, but Cu removals increased with decreasing temperatures. This was explained by increased biological activities in the filters at warmer temperatures, which may have led to an increased release of Cu with dissolved organic matter originating from root turnover and decomposition of organic litter and debris. Furthermore, plant uptake and biofilm adsorption may also be influenced by temperature. However, even in the worst case (i.e. at 20°C), Cu was removed effectively from the stormwater. Further research needs were identified including the effects of road salts on stormwater biofiltration during the winter period.     

Mechanisms of phosphate retention by calcite: effects of magnesium and pH

Purpose

Sorption and precipitation of phosphate are important processes in controlling fate of phosphorus (P) in P-fertilized soils, especially those affected by magnesium (Mg) ions.

Materials and methods

The interaction between Mg(II) (0.42 and 8.33 mM) ions and phosphate (0.32 and 6.45 mM) at the calcite–water interface were investigated with various pH values from 6.0 to 12.0, using a combination of sorption envelopes, Fourier transform infrared spectroscopy, and X-ray diffraction.

Results and discussion

Amorphous calcium phosphate, dibasic calcium phosphate dihydrate, and hydroxyapatite are formed at high phosphate concentration (6.45 mM) and high pH (>8.0). The presence of low Mg(II) ion level (0.42 mM) had little effect on phosphate sorption. When Mg(II) ions increased to 8.33 mM, phosphate retention was inhibited in the weak acid condition since incorporation of Mg(II) ions kinetically hinders precipitation resulting in greater solubility of calcium phosphate while high pH favors Mg adsorption to provide more =Mg sites and OH functional groups on the surface of calcite, which enhanced the formation of Mg–P phases. The likely mechanism is attributed to the different surface terminations of calcite sorbed by phosphate at pH?<?8.0 and pH?>?8.0 in the presence of Mg(II) ions.

Conclusions

Our experimental results suggested that soil pH, initial concentration of phosphate, and the presence of Mg(II) ions and calcite play an important role to affect the fate of phosphate in P-fertilized soils.     

Removal of Ammonia from Aqueous Solutions,Ground Water,and Wastewater Using Mechanically Activated Clinoptilolite and Synthetic Zeolite-A: Kinetic and Equilibrium Studies

Natural zeolite clinoptilolite and synthetic zeolite Na-A were characterized using XRD and SEM to be used as adsorbents for ammonia from aqueous solutions, ground water, and sewage water. Clinoptilolite was mechanically activated for 2, 4, 6, and 8 h to study the effect of activation in enhancing the adsorption capacity. The adsorption by activated natural zeolite and synthetic zeolite is high pH dependent and achieve the best values at pH?=?7. The adsorption capacity of activated natural zeolite increases with increasing the activation from 2 to 8 h achieving removal percentage close to that obtained using synthetic zeolite. The equilibrium was obtained after 60 min for synthetic zeolite and all the activated natural zeolite (except 2-h-activated product, the equilibrium was achieved after 30 min). The kinetic studies reflected the high fitness of the adsorption results of activated natural zeolite products and synthetic zeolite with pseudo-second-order model rather than the other kinetic models. The obtained isotherms reflected the formation of S-type isotherm curve for the adsorption using mechanically activated clinoptilolite and L-type curve for the uptake using synthetic zeolite. The results represented well with Langmuir model followed by Temkin and Freundlich model for adsorption using synthetic zeolite. The uptake using mechanically activated clinoptilolite can be represented by Temkin model rather than both Langmuir and Freundlich models. Thermodynamic parameters indicate spontaneous endothermic adsorption of ammonia using all the zeolitic products under investigation. Finally, the mechanically activated natural zeolite and synthetic zeolite exhibit high efficiency in the removal of ammonia and other water pollutants from ground water and sewage water.     

Seasonal Variability in Stormwater Quality Treatment of Permeable Pavements Situated Over Heavy Clay and in a Cold Climate

Permeable pavements mitigate the impacts of urbanization on surface waters through pollutant load reduction, both by sequestration of pollutants and stormwater volume reduction through exfiltration. This study examined the non-winter water quality performance of two side-by-side permeable pavements in the Ohio snowbelt. The permeable interlocking concrete pavements were designed to drain impervious catchments 2.2 (large) and 7.2 (small) times larger than their surface area, were located over clay soils, and incorporated the internal water storage design feature. Nutrient reduction was similar to past studies—organic nitrogen and particulate phosphorus were removed through filtration and settling, while dissolved constituents received little treatment. Because of 16 and 32 % volume reductions in the small and large installations, respectively, nutrient loads were often significantly reduced but generally by less than 50 %. Aluminum, calcium, iron, magnesium, lead, chloride, and total suspended solids (TSS) concentrations and loads often increased after passing through the permeable pavements; effluent TSS loads were three- to five-fold higher than influent TSS loads. This was apparently due to seasonal release of clay- and silt-sized particles from the soils underlying the permeable pavement and inversely related to elapsed time since winter. The application of de-icing salt is thought to have caused deflocculation of the underlying soils, allowing particulates to exit with stormwater as it discharged from the underdrain of the permeable pavements. By autumn, both permeable pavements discharged metals and TSS concentrations similar to others in the literature, suggesting the de-icing effects lasted 3–6 months post-winter. Sodium may substantially affect the performance of permeable pavements following winter de-icing salt application, particularly when 2:1 clay minerals, such as vermiculites and smectites, predominate.     

Effect of Humic Acid on the Nitrate Removal by Strong Base Anion Exchanger Supported Nanoscale Zero-valent Iron Composite

To probe the effect of common coexist substances on the nitrate removal by polymeric resin supported nanoscale zero-valent iron composite (D201-nZVI), humic acid (HA) was added into the nitrate removal system to elaborate the different interactions between each two and among all in the system including HA, nitrate, and D201-nZVI. The results showed that the effect of HA on the reduction of nitrate by D201-nZVI was concentration-dependent. At low HA concentration (<?5 mg/L), HA coating formed by the HA adsorption on the surface of the nZVI particles enhanced the dispersion of the particles, which led to a more evenly distribution of nZVI particles in the solution, and thus a higher nitrate reduction activity. When HA concentration was increased to 5 mg/L or more, the competitive adsorption of HA and NO₃^? on the surfaces of the D201-nZVI dominated, and the nitrate removal rate and ammonia nitrogen production were decreased. When the HA concentration reached to a further high level (>?20 mg/L), HA acted as an electron shuttle to accelerate the reduction of Fe(III) to Fe(II) in the D201-nZVI, and thus the nitrate reduction rate was accordingly enhanced. The ammonia production increased by 24.8% at HA concentration of 40 mg/L as compared with that of the control (without addition of HA). This research elucidated the interaction of HA within different HA concentration in the complicate system of anions removal by organic support-nanoscale metal particle composite, which may shade some new light on the potential application of nanoscale zero-valent materials in the practical remediation of natural water.     

Field Performance of Bioretention Systems for Runoff Quantity Regulation and Pollutant Removal

Bioretention systems are of immense importance as they serve as small “sponges” for cities, cutting stormwater runoff, removing pollution, and using precipitation resources. However, performance data for these facilities are generally lacking, particularly at the field scale. This study investigated the runoff quantity regulation and pollutant removal performance of bioswale and rain garden systems from 2014 to 2017. A performance assessment of these facilities demonstrated that anti-seepage rain garden, bioswale-A, and bioswale-B effectively retained inflow volumes by the filter media, reducing runoff volumes by 54.08, 98.25, and 77.65%, respectively, on average, with only two events of overflowing. According to the water quality data in 24 rainfall events, the main pollutant indexes for the new city include total nitrogen and chemical oxygen demand, and the median values for their respective effluent event median concentrations were 1.29 and 40.13 mg/L for anti-seepage rain garden and 1.68 and 74.00 mg/L for bioswale-B systems. The mean values of pollutant removal of the three bioretention systems, except for infiltration rain garden, were 39.8–59.73% (median?=?54.32%), 61.06–72.66% (median?=?73.47%), and 76.67%–88.16% (median?=?80.64%). Meanwhile, outflow volume of water was found to be most influenced by inflow volumes for the bioswales and anti-seepage rain garden. Mass removals were higher than concentrations owing to water volume attenuation. Based on the data of monitored pollution loads, this study estimated the annual pollutant load removal as 75.45 and 90.7% for anti-seepage rain garden and bioswale-B according to the percent of monitoring rainfall depth in total annual precipitation. This study also established the target pollutant service life model on the basis of accumulated annual load and media adsorption capacity. The results of this study will contribute to a greater understanding of the treatment performance of bioretention systems, assisting in the design, operation, and maintenance of them.     

Sediment Retention by Alternative Filtration Media Configurations in Stormwater Treatment

Urban stormwater can be treated by infiltration at the source using systems like permeable paving. A critical component of such a system is the filtration media. Laboratory experiments were conducted using columns and boxes to evaluate the sediment retention efficiencies of different filtration media—crushed Greywacke, Greywacke mixed with 10% sand, and layered Greywacke and sand-Greywacke mix. Sediments of 0.001–6 mm were applied at concentrations of 460–4,200 mg/l along with water at flow rates of 100–900 ml/min. All columns showed between 96 and 91% sediment retention efficiency for single dry sediment applications, with lowered sediment retentions at higher flow rates. Decreasing the sediment loading, applying particles of <38 μm size, and suspending the particles in inflow as opposed to directly applying sediments to the column surface gave lower sediment retention efficiencies of 55 to 89%. Sediment retention primarily occurred in the top 20 mm of all columns and the 50th percentile value of retained sediments was 100–300 μm. The box tests showed little effect of flow and sediment loading on particle retention, with the tests showing an average retention of 93%. Similar to the column tests, the box tests showed lower sediment retention (84 to 88%) for <38 μm sediments and greater retention (approximately 95%) for larger sediments.     

Dynamics of Clay Particles in Non-vegetated Stormwater Biofilters

Stormwater biofilters manage quantity and quality of urban stormwater runoff. Particulate solids from natural and anthropogenic sources accumulate on paved surfaces and eventually reach receiving waters. Retention of suspended solids in stormwater management systems ensures the quality of stormwater runoff to water resources. Stormwater biofilters are similar in most of design parameters to sand filters employed in water treatment systems. The understanding and design of stormwater biofilters are often based on generic models of sand filters. Unlike water treatment sand filters, which are continuously fed, stormwater biofilters operate intermittently with spontaneously alternating wetting and drying cycles. This results in dynamic pollutant removal pattern that employs different mechanisms during and across rainfall events. As such, pilot scale biofilter columns fabricated with a layer of organic material were operated. Removal of suspended solids was very dynamic, where impact of age of filter, antecedent dry days, and inflow quality varied during and across events. Flush of retained solids and filter material occurred during the stabilisation period during each event while very high removal percentages (more than 90%) were observed after stabilisation, during an event. Clogging was not observed due to re-entrainment, re-distribution, and flush of retained solids during intermittent wetting and drying cycles.     

Adsorption of Arsenate on Coarse Loamy Mixed Hyperthermic Fluventic Haplustept Soil of Punjab,Northwest India

A laboratory experiment studied the adsorption of arsenate on coarse loamy mixed hyperthermic Fluventic Haplustept soil of Punjab to serve as cheap materials for removal of arsenic (As) from water with elevated As concentration. The arsenate adsorptions onto soil and soil + iron fillings are described by a two‐region Langmuir isotherm equation; that is, the plots showed two distinct linear portions. The bonding energy and adsorption maxima for arsenate adsorption by soil increased slightly at higher equilibrium temperature of 305 K relative to 280 K in the Langmuir plot for region I but followed an appreciative decline in both parameters for region II. The addition of iron fillings enhanced the adsorption maxima of arsenic soils by 2.5‐fold because of physical adsorption and 4.44‐fold because of chemisorptions or precipitation at weak and strong As concentrations, respectively, in soil–water equilibrated systems. Thus, the results of the present investigation suggest that water withdrawn from shallow aquifer containing elevated As concentrations should be equilibrated with mixtures of soil and iron fillings for removal of As. After an equilibration period, separation of water by decantation or filtration could be used for drinking purposes for humans and domestic animals.     

Study of Phosphorus Removal by Using Sponge Iron Adsorption

Phosphorus is one of the key elements causing lake eutrophication. This paper deals with phosphate removal by Sponge iron in batch and fixed-bed operation. Isotherm and kinetic studies are conducted. The isotherm data is described by the Freundlich and Langmuir model, while the kinetic data of adsorption is fitted by the pseudo-second-order kinetic model. The saturated adsorption capacity of Langmuir isothermal equation is about 3.25 mg/g. The concomitant anions have adverse effect on phosphate adsorption and the effects follow the order: NO₃^??>?Cl^??>?SO₄^2?. The phosphate adsorption capacities of SI were improved significantly under the acidic condition. The results of the fixed-bed operation show that, with the increase of the influent phosphate concentrations, the breakthrough curve becomes steeper while the break point time decrease. According to the Adams–Bohart model, the critical height of the column decrease from 0.135 to 0.105 m when the contact time increased from 10 to 30 min with the influent concentration of 1.0 mg/L. According to BDST model, the critical bed depth is 0.15 m when the influent concentration of phosphate is 1.0 mg/L and the contact time (h) is 20 min.     

Nutrient Reduction in Stormwater Pond Discharge Using a Chamber Upflow Filter and Skimmer (CUFS)

Stormwater runoff is a known pollutant source capable of causing surface water degradation, especially in highly populated areas such as Central Florida. Wet detention ponds manage this stormwater, but most of the ponds do not remove enough nutrients, specifically nitrogen and phosphorus, to meet total maximum daily load regulations. This paper presents the use of a chamber upflow filter and skimmer (CUFS) filled with a specific green sorption medium as process modification of stormwater retention ponds, which can increase the removal of nitrogen and phosphorus in the stormwater runoff. Green sorption medium consists of recycled and natural materials that provide a favorable environment for pollutant removal. Water enters the system through the skimmer, which floats on the surface of the detention pond. It travels from the skimmer to the bottom of the chamber where heavier particles settle out before entering the upflow filter. The upflow filter contains 61 cm (24 in.) of green sorption medium providing physicochemical and microbiological processes to remove nitrogen and phosphorus under anoxic/anaerobic conditions. After this treatment, water flows up through the filter and out of the system and eventually travels to Lake Jesup, a eutrophic lake in Central Florida. A total of 28 storm events and seven baseflows were sampled from the site in Seminole County, and ten storm events were sampled from a pilot study of CUFS for statistical analysis and performance evaluation. Significant reductions by the CUFS were confirmed in terms of turbidity, orthophosphorus, total phosphorus, and total suspended solids when the mean values were compared at a 95% confidence level. Reductions also occurred for total nitrogen (TN), but could not be proved by the mean comparison in the field test, whereas the pilot-scale application of the CUFS proved effective for reducing TN at a 95% confidence level. Hydraulic retention time should be increased so as to improve the design for TN removal in future applications.     

不同人工湿地基质对磷的吸附性能研究

通过基质磷素吸附动力学、等温吸附以及基质饱和吸附后磷素解吸实验,研究陶瓷滤料、红泥、水洗砂、炉渣4种人工湿地基质净化磷素的效果,评价其基质磷素饱和吸附后磷素解吸可能造成的二次污染风险。结果表明,在溶液磷（P）浓度为5-150mg·L·^-1条件下,Langmuir和Freundlich等温吸附方程均能很好地描述陶瓷滤料和红泥两种基质的磷素吸附过程,陶瓷滤料用Langmuir方程比Freundlich方程的拟合程度更好,红泥则相反。4种基质对磷素的吸附量顺序依次为红泥〉陶瓷滤料〉炉渣〉水洗砂。从磷素的解吸率来看,4种基质释磷顺序依次为炉渣〉水洗砂〉陶瓷滤料〉红泥,水洗砂和炉渣吸附磷素后的解吸率较高,其他两种基质磷素解吸的比例很低。综合评价,陶瓷滤料更适合作为人工湿地污水除磷的基质。     

Phosphorus Sorption in Hydromorphic Soils Overlying Alluvium and Coastal Plain Sand Parent Materials in Delta State,Nigeria

Highly weathered soils of the tropics are known to have great affinity for phosphate sorption with reportedly high values for affinity constant, k. This study evaluated soil samples from profiles dug at Agbor, Kwale, and Otegbo which overly alluvium and coastal plain sand parent materials for their capacities to sorb phosphorus (P). The samples were equilibrated in 30 ml of 0.01 M calcium chloride (CaCl₂) containing various amounts of P as monopotassium phosphate (KH₂PO₄) to give 0, 25, 50, 100, 150, 200, 400, 800, and 1000 μg/L P for 6 days at a temperature of 25 ± 2°C. The rate of P adsorption increased with increased concentrations of P and was generally low in the soils. Affinity constant k was also low and did not compare with values earlier obtained for well-drained soils. P adsorption capacity decreased in the order: Agbor > Otegbo > Kwale. Percent phosphorus sorbed was highest at Agbor with values of 11.33%, 10.8%, and 10.12% for 50, 100, and 150 mg/kg P added, respectively. The adsorption maxima (b) of the soils was significantly correlated with the soils organic carbon with r = 0.817, p < 0.05; r = 0.883, p < 0.05, and r = 0.886, p < 0.05 for Agbor, Kwale, and Otegbo soils, respectively. Proper management of the soils organic matter content coupled with the addition of rock phosphate is recommended for P improvement in these soils for sustained cultivation of crops such as Raphia hookeri that are adapted to hydromorphic environment.     

Combining Sewage Sludge and Clam Shell Waste to Prepare Adsorbents for Efficient Phosphorous Removal

Effluents containing phosphorous as phosphate ions are frequently discharged in freshwater resources contributing to the eutrophication and directly interfering in the biological equilibrium. Clam shell residues and sewage sludge were combined for preparing efficient adsorbents for phosphate removal from aqueous medium. The adsorbents were characterized before and after adsorption testing, and the adsorption equilibrium and kinetics were investigated. Phosphate removal of 89?±?1% was attained for samples prepared with 0.1?< X <?1.0, where X corresponds to sewage sludge/clam shell mass ratio. The analyses of the experimental errors indicated that the phosphorous removal followed the Elovich kinetic model, which describes adsorption in very heterogeneous surfaces. On the other hand, the best modelling was achieved using the Koble–Corrigan isotherm model, which incorporate different aspects of both Langmuir and Freundlich isotherms to represent the equilibrium data. The observed adsorption capacity (21.4 mgP g^?1) are comparable or greater to that observed for other adsorbents described in the literature.     

Adsorption of Dioxin by Bag Filter + Powdered Activated Carbon

A novel bag filter + powdered activated carbon technique is here proposed to address the low utilization rate of powdered activated carbon and the low dioxin removal rate associated with the conventional activated carbon injection + bag filter technique, better known as the fly ash + activated carbon + bag technique. In this method, dibenzofuran serves as a dioxin simulant. The effect of the adsorption temperature and dibenzofuran inlet concentration on the adsorption performance of activated carbon was studied using a filter cloth adsorption device with an inner diameter of 25 mm, and the adsorption performances of fly ash, activated carbon, and fly ash +5% activated carbon were compared. The results showed that activated carbon exhibited a higher adsorption efficiency and remained highly efficient longer than fly ash +5% activated carbon. When the dibenzofuran inlet concentration was 0.0956 g/m³ (about one million times the concentration of dioxin in the flue gas of incinerated waste), the duration of the high-efficiency (>90%) adsorption of the powdered activated carbon (thickness 1.2 mm) on the filter cloth was over 7 h. These results prove that the replacement of fly ash + activated carbon + filter bag with powdered activated carbon + bag filter can significantly improve the removal efficiency of the dioxin in waste incineration flue gas and the utilization rate of activated carbon.     

Use of Modified Zeolites for the Remediation of Waters and Cultivated Soils from Cu(II)

The ability of iron oxides (goethite) and natural zeolite (clinoptilolite) to adsorb copper from its aqueous solutions was extensively studied in the past. In this paper, the production of modified zeolites (systems I and II) from raw materials of zeolite and goethite was investigated compared to the initial materials. These two systems presented higher adsorption than goethite or clinoptilolite. Comparing the two systems, system II presented higher adsorption than system I. Isotherm studies showed that the adsorption data from all materials were best described by Freundlich isotherm. According to thermodynamic study, the values of ??G° became more negative with the increase of temperature, indicating that the adsorption process was more favorable to higher temperature. The positive values of ??H° indicated endothermic nature of adsorption. The use of all adsorptive materials as soil improvements was also investigated. Goethite, zeolite, and systems I and II were mixed separately with three different soils (clay loam, sandy loam, and loamy sand). Lettuces were cultivated, and the combination of system II with the loamy sand soil led to the best morphological characteristics of lettuces with the minimum adsorption of copper. Consequently, modified zeolites could be considered as two satisfactory detergents of highly copper concentration in soil and water.     

Evaluation of sugar beet pulp efficiency for improving the retention of copper in stormwater basin

Purpose

Sugar beet pulp (SBP) has been shown to be a promising low-cost sorbent for the removal of metals from contaminated waters. The objective of this study was to investigate the impact of SBP addition to horizontal-flow gravel filters in increasing the copper (Cu) retention ability of stormwater basins.

Material and methods

Small-scale gravel filters filled with 6 kg of a sand–sediment mix (SS) were used to experimentally treat Cu-contaminated water under conditions that represented an intense storm event. Sugar beet pulp efficiency was assessed by adding 100 g of raw SBP. Two ways of applying SBP were tested: (1) mixed with SS into the gravel filter or (2) packed at the outlet in a PVC column. Eluates were characterized by their volume, pH, Cu and dissolved organic carbon (DOC) concentrations.

Results and discussion

When placed at the outlet, SBP fixed 73 % of the Cu remaining in solution and increased the overall retention capacity of the gravel filter to 99.4 %. Conversely, when SBP was mixed with SS, the outflowing water carried higher concentrations of Cu and DOC. Complementary batch experiments underlined the crucial role of DOC in the decline of Cu sorption ability observed when SS and SBP were mixed. Geochemical calculations suggested that DOC (assumed to be pectins) promotes the mobilisation of Cu from SS by complexing it in porewater.

Conclusions

Accompanied with careful guidance, SBP has the potential of removing dissolved Cu from contaminated water in gravel filters. Protocols for SBP preparation and conditions of use should be established so as to promote its sorption efficiency and decrease its release of Cu-complexing compounds like pectins.     

Kinetic and Equilibrium Sorption Studies of Ceftriaxone and Paracetamol by Surfactant-Modified Zeolite

An organo-zeolite was prepared by loading hexadecyltrimethylammonium (HDTMA) onto clinoptilolite and was used to remove ceftriaxone sodium and paracetamol in aqueous solutions. Batch experiments were conducted to perform kinetics and sorption isotherms at 25 °C and 100 rpm. The results indicate that the equilibration times were 24 h for ceftriaxone sodium and 9 h for paracetamol. Furthermore, sorption capacities were 0.7288 and 0.0058 mg/g, respectively. The data were treatment with different models including pseudo first order, second order, and Elovich, the results suggested a chemical adsorption mechanism, and the adsorption equilibrium data for the two drugs show that they follow a linear trend, indicating a partitioning mechanism. Physicochemical properties such as solubility, log Kow, and pka play an important role in the adsorption process. Finally, the values obtained for zero charge point (ZPC) for zeolitic materials were 6.90, 6.94, and 6.90 for natural zeolite (ZN), sodium zeolite (ZNa), and zeolite modified surface at 30 mM HDTMA (ZMS-30), respectively.