Comprehensive evaluation of the integrated membrane contactor-microalgae photobioreactor system for simultaneous H2 purification and CO2 treatment from biomass fermented gases

Biohydrogen (H2) has been identified as a potential renewable energy source to substitute energy-based fossil fuel that can be produced from biomass fermentation. However, carbon dioxide (CO2) is also commonly present in the biogas mixture and must be properly treated as it could contribute to the climate change phenomenon. In this study, an integrated membrane contactor-microalgae photobioreactor system is applied to allow simultaneous H2/CO2 treatment from biomass fermented biogases. A comprehensive evaluation of the effectiveness of the integrated system was investigated by screening the essential operating parameters of the system using One Factor at a Time (OFAT) technique followed by optimization Response Surface Methodology (RSM). Serial investigations of the process parameters, the optimum condition was at a pH of 10 with gas and liquid flow rates at the respective levels of 0.1 L/min and 0.5 L/min, while the microalgae concentration was 0.6 g/L. At these optimum conditions, the H2 purity was found to have increased remarkably, from 69.4% to 83.2%. In a long-term separation performance using the optimized conditions, microalgae solution was found to be capable of sustaining its performance at a longer time with only 2% performance dropped observed within 540 min of the operational time. In conclusion, the use of microalgae in a membrane contactor system could be a promising technique for treating these fermented gases, in a move towards carbon neutrality

Polyaniline composite membranes synthesis in presence of various acid dopants for pressure filtration

Polyaniline is a conductive polymer that is recently used as a material in producing a pressure filtration membrane. Polyaniline can be doped in various acids as dopants of different sizes and shapes to modify its inherent properties to produce membrane with high flux and rejection. This work is aimed to fabricate polyaniline composite membrane in presence of different acids as dopants namely hydrochloric acid, maleic acid, poly(methyl vinylether) acid (PMVEA) and polyacrylic acid (PAA). This polyaniline was coated onto microporous polyvinylidene fluoride (PVDF) support by using a specially fabricated two compartment cell. The field emission scanning electron microscope (FESEM) results show that the morphology of the coated polyaniline on PVDF membrane support is in globular shapes, which elongates at different sizes depending to the acid used. From the thermal analysis, the melting point of polyaniline coated PVDF membrane remains at 260°C, similar as obtained in the pristine microporous PVDF indicating no thermal change upon polyaniline coating. From all membranes prepared, the doped polyaniline membrane possessed a good conductivity value except for polyaniline-PMVEA membrane, which has the lowest value. In terms of the membrane filtration performance, which was measured based on the flux of pure water and polyethylene glycol (PEG) rejection, polyaniline-PMVEA membrane has a high flux and the highest PEG rejection. This result indicates that the conductivity does not influence much on the membrane filtration performance, but rather due to the physical coating itself. Different acid dopants present during polyaniline coating will lead to different filtration performance

Comparison of separation performance of absorption column and membrane contactor system for biohydrogen upgraded from palm oil mill effluent fermentation

The adverse effects of ammonia found in wastewater streams lead to the development of advanced water treatment technology, i.e. membrane contactor (MC). In this study, single layer hollow fibre membrane (SLZK) and dual layer hollow fibre membrane (DLZK) were prepared from zirconia and kaolin and modified into hydrophobic membrane through simple grafting process via fluoroalkylsilane (FAS) agent. The properties of membranes such as morphology, surface roughness, mechanical strength, wettability and liquid entry pressure were analysed through scanning electron microscopy (SEM), atomic force microscopy (AFM), 3-point bending strength, contact angle and LEPw setup. Finally, the performance of the membranes was also investigated towards ammonia removal via membrane contactor system. Our findings showed that hydrophobicity properties significantly improved for both SLZK and DLZK membranes after grafting modification process as indicated by the increase of contact angle value from 5° and 1° to 132.7° and ~180.0° respectively. Based on the morphological analysis, the surface of DLZK showed more porous structure as compared to the SLZK. In addition, DLZK also displayed the highest mechanical strength and contact angle reading of 125 MPa and ~180° respectively. This suggests that the DLZK showed an excellent membrane contactor performance with highest value of mass transfer coefficient (3.77 x 10-5 ms-1) and almost complete removal of ammonia removal (91%). Overall, these results implied that dual layer ceramic membrane developed from kaolin and zirconia could provide the basis for the development of alternative ceramic membrane with excellent properties for membrane contactor system

Eco-Friendly Coagulant versus Industrially Used Coagulants: Identification of Their Coagulation Performance, Mechanism and Optimization in Water Treatment Process

The evaluation of complex organic and inorganic coagulant’s performances and their relationships could compromise the surface water treatment process time and its efficiency. In this work, process optimization was investigated by comparing an eco-friendly chitosan with the industrially used coagulants namely aluminum sulfate (alum), polyaluminum chloride (PAC), and aluminum chlorohydrate (ACH) in compliance with national drinking water standards. To treat various water samples from different treatment plants with turbidity and pH ranges from 20–826.3 NTU and 5.21–6.80, respectively, 5–20 mg/L coagulant dosages were varied in the presence of aluminum, ferum, and manganese. Among all, 10 mg/L of the respective ACH and chitosan demonstrated 97% and 99% turbidity removal in addition to the removal of the metals that complies with the referred standard. However, chitosan owes fewer sensitive responses (turbidity and residual metal) with the change in its input factors (dosage and pH), especially in acidic conditions. This finding suggested its beneficial role to be used under the non-critical dosage monitoring. Meanwhile, ACH was found to perform better than chitosan only at pH > 7.4 with half dosage required. In summary, chitosan and ACH could perform equally at a different set of optimum conditions. This optimization study offers precise selections of coagulants for a practical water treatment operation

Durable pressure filtration membranes based on polyaniline-polyimide P84 blends

A pressure filtration membrane from conducting polymer polyaniline (PANI) is known to possess low mechanical strength and thermal stability. Therefore, it is believed that the properties of the membrane can be enhanced by blending PANI with a conventional polymer like polyimide (PI), which possesses high mechanical strength and thermal stability. A thermal analysis revealed that polymer chain of blend membranes started to break beyond the melting temperature of pure PANI membrane indicating that the addition of PI hindered the degradation of PANI and thus slowed down the decomposition process. Mechanical tests further showed that PANI/PI membrane had a tensile strength that was 60% higher than pure PANI membrane. Furthermore, the surface hydrophilicity and negativity of the blend membrane increased as it was doped in acid, thereby reflecting the exploitation of advantages of both polymers. Rejection at various molecular ranges of PEGs showed that PANI/PI membrane was initially in the ultrafiltration (UF) range, but later fell into the nanofiltration (NF) range when an acid dopant was introduced to the membrane. According to the long-term filtration performance, the PANI/PI membrane was able to sustain a rejection of up to 99% in Congo red solution with just a slight reduction in flux

Suatu ulasan kritis kajian keperluan pemfluoridaan air di dalam proses rawatan air

Pemfluoridaan air merupakan proses penambahan bahan fluorida di dalam sumber air terawat sehingga tahap fluorida di dalam air tersebut mencapai tahap yang disarankan oleh pihak berkuasa dan seterusnya memberi manfaat kepada pengguna untuk kebaikan gigi dan tulang. Kementerian Kesihatan Malaysia (KKM) telah mengesyorkan julat nilai kepekatan dos fluorida dalam sistem air di Malaysia adalah dalam lingkungan nilai 0.4 mg/L hingga 0.6 mg/L. Ion fluorida bukanlah suatu keperluan bagi pertumbuhan manusia tetapi dianggap penting untuk mengelakkan kerosakan gigi dan tulang, terutamanya kepada kanak-kanak. Kajian kritis yang telah dijalankan ini memfokuskan kepada keperluan pemfluoridaan air terawat di dalam proses rawatan air. Berdasarkan kajian ini, kandungan unsur fluorida dalam air mentah mempengaruhi proses pemfluoridaan air memandangkan kandungan unsur tersebut di dalam air minuman tidak boleh melebihi had yang ditetapkan oleh pihak berkuasa. Terdapat beberapa jenis bahan berfluorida yang biasa digunakan bagi pemfluoridaan air, antaranya natrium fluorida, natrium silikofluorida dan asid fluorosilisik. Penambahan bahan berfluorida ini ke dalam air hendaklah mematuhi dos yang tepat bagi memberi manfaat kepada pengguna dan seterusnya mengelakkan penyakit berkaitan fluorida. Kesimpulannya, pengawasan yang berterusan terhadap kepekatan fluorida pada pelbagai peringkat sama ada dalam peringkat pengumpulan air mentah, rawatan air dan pengagihan air terawat adalah penting bagi memastikan air dengan kandungan fluorida yang optimum dapat dibekalkan kepada pengguna