Hanapi Mat

For over a century, enzyme immobilisation has been proven to be a superior strategy to improve catalytic activity and reusability and ensure easy separation, easy operation, and reduced cost. Enzyme immobilisation allows for an easier separation of the enzyme from the reaction mixture, thus simplifying downstream processing. This technology protects the enzyme from degradation or inactivation by harsh reaction conditions, making it more robust and suitable to be used in various applications. Recent strategies of immobilisation methods, such as adsorption, cross-linking, entrapment or encapsulation, and covalent bonding, were critically reviewed. These strategies have shown promising results in improving enzyme stability, activity, and reusability in various applications. A recent development in enzyme immobilisation in nanomaterials and agrowaste renewable carriers is underlined in the current review. Furthermore, the use of nanomaterials and agrowaste carriers in enzyme immobilisation has gained significant attention due to their unique properties, such as high surface area, high mass transfer, biocompatibility, and sustainability. These materials offer promising outcomes for developing more efficient and sustainable immobilised enzymes. This state-of-the-art strategy allows for better control over enzyme reactions and enhances their reusability, leading to more cost-effective and environmentally friendly processes. The use of renewable materials also helps to reduce waste generation and promote the utilisation of renewable resources, further contributing to the development of a circular economy.

In this study, cellulose was extracted from waste paper using alkaline and bleaching treatments. The flocculation performance of six quaternized cellulose (QC) samples (QC-1, QC-5, QC-10, QC-15, QC-20, and QC-30) was evaluated through kaolin suspension using the standard jar test method at varying flocculant dosages, kaolin concentrations, pH values, and settling times. The cellulose content of the waste paper and extracted celluloses were 68.6% and 78.1%, respectively. Fourier-transform infrared spectroscopy, x-ray diffraction, thermogravimetric analysis, and scanning electron microscopy showed that the waste paper properties changed after chemical treatment, confirming that the extracted product was cellulose. The QC derivatives were homogeneously synthesized by reacting the extracted cellulose with 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPTAC) in the aqueous medium of sodium hydroxide/urea. QC-15 exhibited a highly effective flocculation capability (99.67%) compared to alum (83.91%), with good performance in a wide pH range. The flocculation kinetics (kNo: 5.9 × 10^−1 s-1) supported this finding. QC-15 removed 99.67% of turbidity compared to alum (83.9%). Besides, filtration of the conditioned sludge with QC-15 was relatively easy, with low specific resistance compared to the commercial alum. Overall, Q-15 was an effective and environmentally friendly flocculant with potential application for treating drinking water.

The utilization of natural zeolite (NZ) as an adsorbent for NH₄⁺ removal was investigated. Three types of NZ (i.e., NZ01, NZ02, and NZ03) were characterized, and their NH₄⁺ adsorption process in aqueous solution was evaluated. The effect of pH towards NH₄⁺ adsorption showed that the NZ01 has the highest NH₄⁺ adsorption capacity compared with other natural zeolites used. The application of NZ01 for a simultaneous removal of NH₄⁺ and turbidity in synthetic NH₄⁺-kaolin suspension by adsorptive coagulation process for treating drinking water was studied. The addition of NZ01 into the system increased the NH₄⁺ removal efficiency (η_NH4+) from 11.64% without NZ01 to 41.86% with the addition of 0.2 g L⁻¹ of NZ01. The turbidity removal (η_T), however, was insignificantly affected since the η_T was already higher than 98.0% over all studied parameter’s ranges. The thermodynamic and kinetic data analyses suggested that the removal of NH4⁺ obeyed the Temkin isotherm model and pseudo-second-order kinetic model, respectively. Generally, the turbidity removal was due to the flocculation of destabilized solid particles by alum in the suspension system. The η_NH4+ in surface water was 29.31%, which is lower compared with the removal in the synthetic NH₄⁺-kaolin suspension, but a high η_T (98.65%) was observed. It was found that the addition of the NZ01 could enhance the removal of NH₄⁺ as well as other pollutants in the surface water.

Quaternized lignin-based flocculant (QL) was prepared by a single-step reaction of an extracted lignin (EL) derived from oil palm empty fruit bunches (OPEFB) with 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPTAC) under alkaline condition. The performance of QLs was studied for various β values (molar ratios of CHPTAC to phenylpropanoid unit of lignin), flocculant dosages, pH values, kaolin concentrations, slow mixing rates and sedimentation times. The QL10 achieved the highest turbidity removal efficiency (ε_t) with increasing flocculant dosage, pH and kaolin concentration to the optimal conditions of 5 mg L⁻¹, pH 7 and 1000 mg L⁻¹, and required 20 min of sedimentation time at all the mixing rates tested. The flocculation kinetics agreed well with the particle collision model. The QL10 has good sludge dewatering properties compared to the alum. It also showed encouraging results in water quality analysis for sewage wastewater flocculation in comparison to that of the alum. This indicates the potential application of QL in treating water and wastewater.

Lignocellulosic solutions from oil palm empty fruit bunch (OPEFB) organosolv pulping process are used as demulsifiers for demulsification of crude oil emulsion using a model of water-in-oil emulsion of crude oil and brine solution. The results indicate that the demulsification performance was favored when only lignin compound was contained in the demulsifier. The phase separation capacity and rate were strongly affected by brine pH values, temperatures and demulsifier dosages. Complete phase separation capacity was achieved at the optimum conditions. The separated oil and water are qualified for refining process and water treatment, respectively, making it promising as a demulsifier.

The aim of this work is to convert agroforestry residue to a novel adsorbent (M-1CTA-SDS-BT) used for adsorptive benzene sequestration from aqueous solution. In this study, the anionic surfactant-coated-cationized banana trunk was synthesized and characterized for batch adsorption of benzene from aqueous solution. The surface morphology, surface chemistry, surface area, and pore properties of the synthesized adsorbents were examined. It was proven that surface cationization successfully increased the benzene adsorption capacity of sodium dodecyl sulfate-coated adsorbents. The Langmuir isotherm model satisfactorily described the equilibrium adsorption data. The maximum benzene adsorption capacity (q_max) of 468.19 μmol/g was attained. The kinetic data followed the pseudo-second-order kinetic model in which the rate-limiting step was proven to be the film diffusion. The batch-adsorbent regeneration results indicated that the M-1CTA-SDS-BT could withstand at least five adsorption/desorption cycles without drastic adsorption capacity reduction. The findings demonstrated the adsorptive potential of agroforestry-based adsorbent as a natural and cheap material for benzene removal from contaminated water.