Daofang Zhang

Preparation of sewage sludge based activated carbon by using Fenton's reagent and their use in 2-naphthol adsorption.

In this study, Fentons reagents (H2O2/Fe(2+)) are used to activate raw sewage sludge for the preparation of the sludge based activated carbon. The effect of the amount of hydrogen peroxide addition on carbons chemical composition, texture properties, surface chemistry and morphology are investigated. Choosing an appropriate H2O2 dosage (5 v%) (equivalent to 70.7 mM/(g VS)), it is possible to obtain a comparatively highly porous materials with SBET and the total pore volume being 321 m(2)/g and 0.414 cm(3)/g, respectively. Continuously increasing the oxidant ratio resulted in a decreased SBET value. Further adsorption experiments by using 2-naphthol as model pollutant revealed that the adoption followed a pseudo-second-order kinetics better than pseudo-first-order. The calculated adsorption capacity is 111.9 mg/g on the carbon with 5% H2O2 pretreatment while this value is just 51.5mg/g on carbons without any pretreatment.

A comparative study of aerobically digested and undigested sludge in preparation of magnetic chars and their application in 1-diazo-2-naphthol-4-sulfonic acid adsorption.

In this work, two types of sewage-sludges, aerobically digested and undigested sewage sludge, were used as precursors in the preparation of chars with magnetic property. The two solids were characterized to establish their textural and chemical properties. Due to different elemental composition, chars from the digested sludge were found to contain zeolite-like minerals such as NaP1 zeolite, which enables its abilities of anion exchange, while chars from undigested sewage sludge exhibited a well-degreed graphite structure. 1-Diazo-2-naphthol-4-sulfonic acid (1,2,4-Acid) was used as a model pollutant to investigate its adsorption on prepared chars. The adsorption kinetics of 1,2,4-Acid onto both chars followed pseudo-second-order kinetics. The simulated Langmuir-Freundlich model illustrated that the equilibrium adsorption amount of 1,2,4-Acid was 102.8 and 105.3mg/g, respectively, at 303 K. The adsorption amount declined on digested chars, whereas kept stable on the other in the presence of sodium chloride, suggesting the diversity in adsorption behavior.

Nanoscale iron oxides loaded granular activated carbon (GAC-NSIO) for cadmium removal

AbstractA new hybrid material was prepared by loading the nanoscale iron oxide particles within the pores of granular activated carbon (GAC-NSIO) and used as adsorbent to remove Cd(II) in aqueous phase. The new material is characterized by the pHpzc, TEM, XRD, BET, and XPS analytical techniques to deduce the potential adsorptive mechanism, and further it along with GAC were assessed in the removal of Cd(II) from aqueous solution for various physico-chemical factors iron-loaded content, pH, humic acid, isotherm, kinetics, and thermodynamics, under the batch reactor studies and rapid small-scale column tests also appended dealing with the breakthrough volume. Characterization of adsorbent indicated that the amorphous nanoscale iron oxides were successfully immobilized on GAC. Adsorption mechanism mainly included surface complexation, Donnan membrane effect, and electrostatic attraction. The optimum iron-loaded content of GAC-NSIO was 17%. The adsorption process was more favorable at high pH, and iron oxide ...

Effect of overlying water pH, dissolved oxygen and temperature on heavy metal release from river sediments under laboratory conditions

Abstract The heavy metal release experiments were conducted in the laboratory to examine the effects of 3 factors - pH, dissolved oxygen (DO), and temperature on the metal release from sediments taken from the Huangpu River. The metal concentrations in the dry sediments ranged from 0.030 to 0.296 mg g-1 for Cr, 0.021 to 0.097 mg g-1 for Ni, 0.014 to 0.219 mg g-1 for Cu, 0.035 mg to 0.521 mg g-1 for Zn, 0.0002 to 0.001 mg g-1 for Cd and 0.023 to 0.089 mg g-1 for Pb. Most of the metals found in the sediments were in the form of residual fraction, the exchangeable fraction consisted of only a small portion of total metals. The average dissolved metal concentrations in the overlying water during the 13-day period under different conditions were ranging from 0.82 to 1.93 μg L-1 for Cr, 1.08 to 4.19 μg L-1 for Ni, 40.79 to 82.28 μg L-1 for Cu, 20.30 to 29.96 μg L-1 for Zn, 1.57 to 4.07 μg L-1 for Cd, and 22.26 to 75.50 μg L-1 for Pb, respectively. Statistical interpretation of the data indicated that pH (7, 8, 9), dissolved oxygen DO (1.0 and 5.0 mg L-1) and temperature (4, 16, 25°C) had no significant effects on the heavy metal release under the studied conditions. Cu and Pb had the highest release flux, while Cd, Pb and Cu had higher mobility. The main factors controlling the metals release might be the inherent characters of metals and sediments.