New Generation Material for the Removal of Arsenic from Water - Advanced Materials for Agriculture, Food and Environmental Safety - page 67

Table 3.3 Chars and coals with dif erent parameters.

Adsorbent pH Concentration range Capacity (mg/g)

As(III)

Ref.

As(V)

Hydroxyapatite
and barite or
bone-char

2-5 4-100 mg/L - [62]

Pine wood char
Oak wood char
Oak bark char
Pine bark char

3.5
3.5
3.5
3.5

10-100 μg/L
10-100 μg/L
10-100 μg/L
10-100 μg/L

0.0012 -
0.006 -
0.0074 -
12 -

[63]

3.1.5.4 Red Mud

Red mud has been used for arsenic removal from water. Heat and acid
treatments on red mud increased its adsorptive capacity. Arsenic adsorp-
tion on acid- and heat-treated red mud is also pH dependent, with an opti-
mum range of 5.8-7.5 for As(III) and 1.8-3.5 for As(V) [64]. Adsorption
followed a i rst-order rate expression and i t the Langmuir isotherm well.
Isotherms were used to obtain the thermodynamic parameters. h e As(III)
adsorption was exothermic, whereas As(V) adsorption was endothermic
[65]. Also reported was As(V) removal by using liquid phase of red mud
(LPRM) [66]. Seawater-neutralized red muds (Bauxol) [67], Bauxsol acti-
vated by acid treatment, and by combined acid and heat treatment, and
Bauxsol with added ferric sulphate or aluminium sulphate [68], activated
Bauxsol (AB), and chemically modii ed and activated Bauxsol (AB)-coated
sand [69-70] were all applied to arsenic removal. Modii ed calcined baux-
ite was also used for As(III) and As(V) remediation from groundwater
[71-74] in batch and column modes. h e optimum pH was 7.0 for both
As(III) and As(V). Adsorption was unaf ected by temperature variations.
No appreciable ionic ef ects except from and EDTA were observed from the
background ions including Ca(II), Fe(III), Cl − , , and F − . Sorption capacities
were calculated using the Langmuir model are given in Table 3.4.

3.1.5.5 Blast Furnace Slag

Steel plants generate a large volume of granular blast furnace slag. It is
being used as i ller or in the production of slag cement. Recently, it was
converted into an ef ective and economical scavenger and utilized for the
remediation of aqueous arsenic [75, 76]. Blast furnace slag (BFS) for aque-
ous As(III) remediation has been used. h e maximum As(III) adsorption