Effect of Alkali Treatment on Heavy Metals Adsorption Capacity of Sewage Sludge

Abstract

Sewage sludge is the promising raw material for biosorbent preparation. In this work, we evaluated the heavy metals adsorption characteristics of alkali treated sewage sludge (ATSS) by equilibrium studies. The adsorption isotherms were fitted with Langmuir and Freundlich models. Comparing with untreated sewage sludge, the total adsorption capacity (qm) of ATSS (prepared with 0.125 mol/L NaOH) for Cd, Pb, Ni, increased by 0.51, 0.70 and 0.32 mmol/g, respectively. When the NaOH concentration for ATSS preparation increased from 0.125 mol/L to 0.25 mol/L, the qm of ATSS for Pb decreased from 1.05 mmol/g to 0.84 mmol/g. However, when the NaOH concentration increased from 0.25 mol/L to 7.5 mol/L, it showed increasing trend. According to the IR spectra data, the adsorption effect of biosorbent for heavy metals was mainly due to the complexation of -N-H groups and -COOH groups.

Tolerance and mycoremediation of silver ions by Fusarium solani

“…The new band at 2075.03 cm À1 in the case of NL biomass (Figure 6b), the shift at 1743.2 cm À1 (TL biomass) and 1641 cm À1 are due to the C¼O stretching mode of carbonyl groups in esters, alcohol, ethers and carboxylic acids (Jeyasundari et al, 2017). The marked shift at 1562.06 cm À1 (Δ 18 cm À1 ) (TL biomass) was due to the C-N stretching vibration, N-H bending vibration, and the complexation with N-H group (Hu et al, 2015). This shift indicated that acidic groups; carboxyl and hydroxyl, are the chief agents in uptake (El-Gendy et al, 2017).…”

“…Alkali treatments increase the electronegativity of the fungal biomass by the ionization of functional groups, thus attract more cations Bux and Kasan (1994); Renitta et al (2019). A decrease in biosorption of Ag(I) in alkali-treated biomass was observed that may be due to the hydrolysis and disintegration of biomass by NaOH solution (Hu et al, 2015). The initial metal ion concentration has a fundamental role as a driving force to cope with the mass transfer resistance between the solid and aqueous phases.…”

Mercury and antimony in wastewater: fate and treatment

“…It is acknowledged that biosorbents can remove metals from sludge by ion exchange and adsorption (Hu et al 2015 ). Both these mechanisms are influenced by biosorbent components and operational conditions with lengthened HRT and SRT enhancing technique removal efficiency (Stoveland and Lester 1980 ; Petrie et al 2014 ).…”

“…Ion exchange removal of heavy metals from sewage sludge is however suggested to yield relatively low efficacy (50–60 %), with both gel and macroporous cation exchange resins demonstrating similar effects (De Villiers et al 1995 ). Adsorption mechanisms, applied to sewage sludge, are influenced by SS and organic compounds which in most instances cause media fouling and plugging, therefore requiring pre-treatment with flocculation, settling and filtration or oil-water separation (Hu et al 2015 ). These limitations alongside the influence of colloids are also responsible for membrane fouling (Fu and Wang 2011 ).…”

“…Despite adsorption limitations alkali adsorption treatment has been deployed. Alkali treatment is a biosorbent method to enhance sewage sludge adsorption capacity, increasing complexation through the formation of more ionised functional groups (Hu et al 2015 ). This technique indicates the following bonding affinity trend for alkali-treated sewage sludge to heavy metals Pb 2+ > Cd 2+ > Ni 2+ (Hu et al 2015 ), demonstrating that alkali treatment may effectively remove Hg as this element shows similar binding affinity to Pb (Bailey et al 1999 ).…”