VALORIZATION OF SPENT (CAROTENOID-EXTRACTED) GREEN-MICROALGAL BIOMASS INTO BIOCHAR FOR SIMULTANEOUS REMOVAL OF BRICK-KILN-ASSOCIATED METALS (PB, NI, CD, FE) FROM IMPACTED WATER: RSM OPTIMIZATION, ISOTHERMS, AND REUSABILITY

Amjad Abd Ali Shihad

doi:10.70604/jmtbas.v3i2.201

Authors

Amjad Abd Ali Shihad Ministry of Education, General Directorate of Al-Qadisiyah Education, Diwaniyah 58001, Iraq

Abstract

Heavy metal pollution in water bodies around brick-kiln industries has created a serious environmental problem especially in the developing countries where implementation of rules and regulations is weak. In the present work, spent Chlorella vulgaris biomass, obtained after carotenoid extraction, was converted into biochar (SMBC) via slow pyrolysis at 500 °C and subsequently used as a low-cost adsorbent for the simultaneous removal of lead (Pb), nickel (Ni), cadmium (Cd) and iron (Fe) from simulated brick-kiln-impacted water. The physical characteristics of the biochar were evaluated by FTIR, XRD, SEM-EDX, BET surface area and thermogravimetric analysis (TGA). Response surface methodology (RSM) based central composite design (CCD) was employed to optimise four important process factors i.e. pH, adsorbent dosage, initial metal concentration and contact time. Under optimised conditions of RSM (pH 6.5, dosage 2.0 g/L, concentration 50 mg/L, time 110 min), removal efficiencies of 97.2%, 82.1%, 89.6% and 92.8% were observed for Pb, Ni, Cd and Fe, respectively. The Langmuir isotherm model was found to be well fitted to the equilibrium data for all four metals indicating the monolayer chemisorption on the homogenous active sites. Kinetic investigations revealed that the adsorption process followed pseudo-second-order kinetics. During regeneration trials, SMBC maintained more than 85% of the initial adsorption capacity after 5 adsorption-desorption cycles. The results demonstrate the possibility of a circular biorefinery technique where microalgal biomass is used for two purposes: firstly, as a source of high-value carotenoids and secondly, as a precursor for an effective and reusable heavy metal adsorbent.

Keywords:

Spent microalgal biomass, Biochar, Heavy metals, Brick kiln, Response surface methodology, Adsorption isotherms, Reusability, Circular biorefinery

DOI

https://doi.org/10.70604/jmtbas.v3i2.201

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