Contaminants’ immobilisation of incinerated air pollution control residue and rubber sludge using respectively Calcium Aluminate cement and ordinary portland cement with rice husk ash via stabilisation/solidification technique
Abdul Latif, Abdul Rani
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Treatment of incinerated wastes has become a challenge as the production of these wastes increased each year which become source of hazard to human and ecosystem. Corresponded to that, the first stage of experiment was to treat air pollution control (APC) residue from municipal solid waste (MSW) incineration using two types of calcium aluminate cements (CAC) known as Secar 71 and Ciment Fondu. While the second stage of experiment focused on the treatment of local incinerated waste from rubber gloves industry known as incinerated rubber sludge (IRS) using combination of ordinary Portland cement (OPC) and rice husk ash (RHA) mixtures which comprises of 50% rice husk activated carbon and 50% rice husk ash. The aim of this research is to immobilise heavy metals and non hazardous contaminants such as chlorides and sulphates within these wastes using stabilisation/solidification (S/S) technique. The objectives of this study were to study the effects of waste and RHA addition to compressive strength, to assess the effectiveness of RHA in immobilising the contaminants via analysing the leaching pattern and also to evaluate the stability and disintegration of the mineral phases from the stabilised/solidified sample. Series of factorial design were used to prepare mix formulations for CAC and OPC sample batches. As for APC residue treated with CAC, the focused is more towards incorporating the chlorides and sulphates in respective minerals known as Friedel’s salt and ettringite. Treatment of IRS using OPC was aided by including mixtures of RHA to functional as activated carbon and provide high silica content for enhancing sample strength. Findings on first stage of experiment show that, Friedel’s salt and ettringite were able to be formed successfully to immobilise chloride and sulphate. Whereas the second stage of experiment revealed that, there was reduction in terms of heavy metals and chlorides concentration that leached out from stabilised/solidified sample containing incinerated rubber sludge as RHA been incorporated into the batch samples as compared to OPC with IRS alone. Sulphates were able to be fully immobilised in the presence of RHA in the sample. In terms of unconfined compressive strength, most of the RHA addition batch samples have shown remarkable results as all compressive strength findings surpassed the minimum requirement of sanitary disposal which was at 1 MPa even at 50% waste addition or 1:1 waste to binder ratio. These findings have derived to conclusion that RHA is an excellent material to be included in hazardous waste treatment using S/S whereby the treated waste is also suitable to be reconsidered and utilised as secondary material for construction such as underneath road fillers or base foundation.