Kaolinite and Cd2+ Transport and Interaction in Sand Media: Batch and Column Experiments

Batch sorption and column transport experiments were used to investigate kaolinite colloids and Cd(II) ions (Cd2+) co-transport in water-saturated sand media. Batch sorption was used to evaluate Cd2+ sorption onto kaolinite clay as a function of the initial Cd2+ concentrations and solution ionic strengths as well as determining the equilibrium sorption isotherms. For very low ionic strength (~0 mM), the Langmuir isotherm was the more suitable isotherm for the experimental results while at higher ionic strength (> 0.45 mM) the Freundlich isotherm was the more suitable isotherm. The sorption parameters, KF, KL, n, and qm, were found to decrease with increasing ionic strength. For column transport experiments, Cd2+-bearing kaolinite colloids were found to be retained more in the column for an increase in the solution ionic strength. For example, the steady state breakthrough rate of Cd2+-bearing kaolinite colloids was 0.2 Ci/C0 for an ionic strength of 0.0 mM compared to about 0.05 Ci/C0 for ionic strengths of 0.45 and 0.9 mM. This increased Cd2+-bearing kaolinite colloid retention trend with increased solution ionic strength was likely due to the reduced zeta-potential and increased size of the colloid particles at higher ionic strengths. Consequently, the kaolinite-facilitated Cd2+ concentration decreased with increasing solution ionic strength. In summary, solution ionic strength had a strong effect on the transport behavior of kaolinite-facilitated Cd2+ and Cd2+-bearing kaolinite colloids through the sand column

Pervious Concrete Physical Characteristics and Effectiveness in Stormwater Pollution Reduction

The objective of this research was to investigate the physical/chemical and water flow characteristics of various previous concrete mixes made of different concrete materials and their effectiveness in attenuating water pollution. Four pervious concrete mixes were prepared with Portland cement and with 15% cementitious materials (slag, limestone powder, and fly ash) as a Portland cement replacement. All four pervious concrete mixtures had acceptable workability. The unit weight of the fresh pervious concrete mixtures ranged from 115.9 lb/yd3 to 119.6 lb/yd3 , while the 28 day compressive strength of the pervious concrete mixes ranged from 1858 psi (mix with 15% slag) to 2285 psi (pure cement mix). The compressive strength generally increased with unit weight and decreased with total porosity (air void ratio). The permeability of the four mixes generally decreased with unit weight and increased with total porosity. The permeability coefficients ranged from 340 in./hr for the pure cement mix to 642 in./hr for the mix with 15% slag. The total porosities of the four pervious concrete mixes ranged from 24.00% (mix with 15% slag) to 31.41% (pure cement mix) as measured by the flatbed scanner test method, while the porosities ranged from 18.93% (mix with 15% slag) to 24.15% (pure cement mix) as measured by the RapidAir method. The total porosities of the four pervious concrete mixes measured by the flatbed scanner method were higher than those measured by the Rapid Air method, but the specific surface areas measured by the flatbed scanner method were all lower than those measured by the Rapid Air method. For the pollution abatement experiments, mixes with fly ash and limestone powder removed about 30% of the input naphthalene concentration, while the mix with slag only removed 0.5% of the influent naphthalene concentration. The water volume balance showed that less than 1% of the water added was retained in the experimental column setup

Water conservation through reclamation of sewage for reuse

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Single-Step Fabrication of a Dual-Sensitive Chitosan Hydrogel by C-Mannich Reaction: Synthesis, Physicochemical Properties, and Screening of its Cu²⁺ Uptake

Uncovering the value of waste materials is one of the keys to sustainability. In this current work, valorization of chitosan was pursued to fabricate a novel modified chitosan functional hydrogel using a process-efficient protocol. The fabrication proceeds by a one-pot and single-step C-Mannich condensation of chitosan (3% w/v), glutaraldehyde (20 eq.), and 4-hydroxycoumarin (40 eq.) at 22 °C in 3% v/v acetic acid. The Mannich base modified chitosan hydrogel (CS-MB) exhibits a dual-responsive swelling behavior in response to pH and temperature that has not been observed in any other hydrogel systems. Combining the pre-defined optimal swelling pH (pH = 4) and temperature (T = 22 °C), the CS-MB was screened for its Cu2+ adsorption capacity at this condition. The CS-MB achieved an optimal adsorption capacity of 12.0 mg/g with 1.2 g/L adsorbent dosage after 36 h with agitation. The adsorption of Cu2+ on the surface of CS-MB was verified by EDS, and an overview of the adsorption sites was exhibited by FT-IR. The simply fabricated novel CS-MB hydrogel under investigation presents a unique response to external stimuli that exhibits a promise in heavy metal removal from aqueous media

Ultrafiltration of ink and latex wastewaters using cellulose membranes

Ultrafiltration (UF) studies were conducted on latex and ink rinse wastewaters to assess the potential of concentrating the wastewater and recovering the permeate for reuse and recycling purposes. The physicochemical characteristics of the ink and latex wastewater suggested that the quality of both wastewaters was strongly dependent on the rinse process. A 4-fold and 7-fold concentration of ink and latex wastewater, respectively, may be achieved depending on the initial physicochemical characteristics of the wastewater. The UF system concentrated the latex wastewater to a total solids (TS) concentration of 275 g/L (approx. 28%) and to 99 g/L (approx. 10%) for ink wastewater. The permeates had turbidities ranging from 0.13 to 0.4 NTU. However, a significant percentage of the TS remained in the permeate of the ink wastewater which may require further treatment before it can be reused. For latex wastewater, it is likely that the retentate can be reused along with the permeate for rinsing purposes. For the ink wastewater, both pore blocking and cake resistance models were able to describe the change in flux with time. However, for the latex wastewater, pore blocking seemed to describe the flux with time data better than the cake resistance models. The fouling coefficient, K, for the pore blocking model was found to be a function of the TS present in the latex wastewater. © 2004 Elsevier B.V. All rights reserved

Cation of a full-scale sequencing batch reactor operational mode for biological nutrient removal

WOS: 000255663700009PubMed ID: 18419014Two biological nutrient removal modes, consisting of anaerobic, anoxic, and oxic sequences, were tested in a full-scale sequencing batch reactor. The modes, identified as BNR-S1 and BNR-S2, had average total nitrogen removals of 84 and 89%, respectively, for the months of August to October. Over the same period, total phosphorus removals for BNR-S1 and BNR-S2 were 88 and 87%, respectively. In contrast, total nitrogen and total phosphorus removals for the regular aerobic mode were 54.7 and 44.7%, respectively. When the wastewater temperature changed from approximately 20 to 15 degrees C in the winter months, total nitrogen and total phosphorus removals for BNR-S2 were reduced to 81 and 70%, respectively. Total nitrogen effluent concentrations were between 2.5 and 4 mg-N/L (at approximately 20 degrees C), while the effluent total phosphorus concentrations were between 1 and 2 mg/L. The BNR-S2 mode was found to require less energy per kilogram of soluble chemical oxygen demand removed than the regular and BNR-S1 modes

Evaluating the toxicity of hydroxyapatite nanoparticles in catfish cells and zebrafish embryos

The toxicity of needle-(nHA-ND) and rod-shaped (nHA-RD) hydroxyapatite (HA) nanoparticles is evaluated in vitro on catfish B-cells (3B11) and catfish T-cells (28s.3) and in vivo on zebrafish embryos to determine if biological effects are similar to the effects seen in mammalian in vitro systems. Neither nHA-ND nor nHA-RD affect cell viability at concentrations of 10 to 300 μg mL−1. However, 30 μg mL−1 needle-shaped nHA lower metabolic activity of the cells. Axial deformations are seen in zebrafish exposed to 300 μg mL−1 needle shaped nHA after 120 h. For the first time, nHA is reported to cause zebrafish hatching delay. The lowest concentration (3 μg mL−1) of both types of nHA cause the highest hatching inhibition and needle-shaped nHA exposed zebrafish exhibit the lowest hatch at 72 h post fertilization