In this work, the removal of Methyl Orange (MO) from aqueous solution was studied using a new nonconventional
and eco-friendly adsorbent, spent tea leaves (STL). Untreated and acid treated STL were
used as bio-adsorbent for removal of MO using batch method. Effects of different STL dosages (1 – 4
g), pH solutions (2–11) and initial dye concentrations (10 – 60 mg/L) were investigated. Adsorption
experiments conducted using acid treated STL resulted in higher MO removal efficiency ranging from
79 to 92% for 1-4 g of adsorbent dosage compared to the untreated ones which resulted in only 18 to
56% of removal for the similar amount of dosage. In addition, acidic condition favours the MO removal
as compared to alkaline medium. Experimental data were analysed using the Langmuir and Freundlich
models of adsorption and it was found that adsorption isotherm was best described by Freundlich model
and pseudo-first order equation with high correlation coefficient. Results revealed that acid treated STL,
being a waste, has the greater potential to be used as adsorbent for MO removal from aqueous solution.
In this study, solidification/stabilization (S/S) of nickel hydroxide sludge using ordinary Portland cement (OPC) and oil palm ash (OPA) was carried out. The effects of increased substitution of OPA wt% in the S/S mix designs on the treated samples' physical and chemical characteristics were investigated. The physical characteristics studied were unconfined compressive strength (UCS) and changes in crystalline phases while chemical characteristics studied were leachability of nickel and leachate pH. Results indicated the optimum mix design for S/S of nickel hydroxide sludge using both OPC and OPA at B/S(d)=1 in terms of cost-effectiveness and treatment efficiency was 15 wt% OPA, 35 wt% OPC and 50 wt% sludge. The sufficient UCS and low leached nickel concentrations shown for this mix design indicate the viability of using OPA as substitute of OPC as it can significantly reduce cost normally incurred by usage of high amounts of OPC.