Sisa Pepejal dan Pengurusan Hijau

Alam semula jadi merupakan ciptaan Tuhan yang sangat bernilai dan manusia telah dipertanggungjawabkan untuk memelihara dan memuliharanya. Namun demikian, alam sekitar semakin terancam disebabkan oleh keghairahan mengejar arus pembangunan, pemodenan, harta benda dan sikap acuh tidak acuh oleh segelintir manusia. Salah satu contoh yang paling ketara ialah penghasilan sisa atau sampah oleh individu di setiap pelusuk dunia. Sisa atau sampah telah menjadi aspek yang penting dalam kehidupan harian setiap individu. Ianya tidak dapat dipisahkan daripada diri kita. Semestinya, penghasilan sisa harus diseimbangkan dengan tabiat pengurusan sisa. Pengurangan dan pengurusan sisa penting untuk merealisasikan konsep pengurusan hijau dan kelestarian alam sekitar. Setiap insan perlu memainkan peranan dan bertanggungjawab dalam menguruskan sisa yang dihasilkan bagi memastikan bumi ciptaan Tuhan yang Maha Esa ini selamat, terpelihara dan terpulihara serta terjamin kesejahteraannya untuk manusia sejagat dan juga generasi yang akan datang. Matlamat utama buku ini adalah sebagai panduan mengenai aspek-aspek penting dalam pengurusan sisa dan hijau. Pengurusan sisa secara sistematik, efisien dan lestari dapat menjamin kehijauan dan keaslian muka bumi ini. Di samping itu, kehijauan dan kelestarian alam sekitar juga secara langsung mendatangkan pelbagai nikmat dan manfaat kepada semua individu. Masyarakat seluruhnya, sama ada kanak-kanak mahupun golongan tua perlu mempunyai ilmu pengetahuan dalam pengurusan sisa. Ini akan membantu mereka mengambil langkah yang betul dalam menguruskan sisa sama ada sisa pepejal atau bahan yang boleh dikitar semula dengan cara yang betul. Buku ini dibahagikan kepada lima bab. Bab 1 memberikan gambaran tentang keseriusan isu penghasilan dan pembuangan sisa secara amnya. Pengenalan kepada sisa pepejal, kadar penghasilan sisa tersebut dan faktor-faktor yang mempengaruhi penghasilan sisa diketengahkan dalam Bab 2. Takrifan sisa pepejal, komposisi sisa, kesan-kesan pengurusan sisa yang tidak efisien, cabaran-cabaran pengurusan sisa pepejal, contoh kajian kes, dan hubungkait di antara pengurusan sisa pepejal dengan Sasaran Pembangunan Lestari (SDGs) pula telah dibincangkan dalam Bab 3. Bab 4 pula menggariskan aspek-aspek mengenai kitar semula seperti bahan-bahan yang boleh dikitar semula, dan cabaran-cabaran utama yang menjadi halangan kepada kejayaan kitar semula di Malaysia. Bab ini juga memfokuskan kepada plastik yang merupakan antara sisa yang paling banyak dihasilkan, pencemaran plastik dan mikroplastik serta isu penggunaan pelitup muka. Bab yang terakhir iaitu Bab 5 mengupas konsep atau kaedah pengurusan hijau, dasar teknologi hijau negara, konsep pengomposan dan pengomposan Takakura, dan projek penghijauan komuniti dan pembangunan komuniti

Recent advances in TiO2/ZnS-based binary and ternary photocatalysts for the degradation of organic pollutants

Semiconductor-mediated photocatalysis plays a pivotal role in the elimination of organic pollutants from water systems. Titanium dioxide (TiO2) and zinc sulphide (ZnS) semiconductors are commonly utilized as photocatalysts in water purification due to their physical and chemical stability and also large band gap. The drawbacks of both semiconductors,nevertheless, prevent them from being used in real and large-scale treatments. Therefore, binary and ternary-based TiO2/ZnS nanostructured materials may be a promising solution to improve the quantum efficiency, structural, and electrical features of pure TiO2 and ZnS semiconductors for improved photoefficiency. This review aims to unravel the development of binary TiO2/ZnS and the modification of ternary photocatalysts (TiO2/ZnS-X, X =metal, non-metal, and dye sensitization) by various approaches. The engineered TiO2/ZnS-based ternary nanostructured materials have exhibited exceptional performance to accelerate the degradation of organic pollutants in wastewater.These materials were fabricated by modifying TiO2/ZnS binary composite and embedding co-catalysts like carbonaceous material, polymeric material, transition metal, metal oxide, and metal. The relationship between the properties of the resulting nanomaterials and their photocatalytic performances has been examined. This review has also placed a special focus on the synthetic routes applied to derive the binary and ternary TiO2/ZnS composites. Another aim of this review is to scrutinize the factors that influence the performance of binary and ternary-based TiO2/ZnS composites on the degradation of organic pollutants. Opportunities for further investigation have been also outlined, along with limitations and impediments based on the current findings

TiO2 photocatalysis of naproxen: Effect of the water matrix, anions and diclofenac on degradation rates

The TiO2 photocatalytic degradation of the active pharmaceutical ingredient (API) naproxen (NPX) has been studied using a laboratory-scale photoreactor equipped with a medium pressure mercury lamp. UV/TiO2 photocatalysis proved highly efficient in the elimination of NPX from a variety of water matrices, including distilled water, unfiltered river water and drinking water, although the rate of reaction was not always proportional to TiO2 concentration. However, the NPX degradation rate, which follows first-order kinetics, was appreciably reduced in river water spiked with phosphate and chloride ions, a dual anion system. Addition of chloride into drinking water enhanced the TiO2-photocatalysed degradation rate. Competitive degradation studies also revealed that the NPX degradation was greatly reduced in the presence of increased concentrations of another API, diclofenac (DCF). This was established by (i) the extent of mineralization, as determined by dissolved organic carbon (DOC) content, and (ii) the formation of intermediate NPX by-products, identified using liquid chromatography and electrospray ionization (positive and negative mode) mass spectrometry techniques. This study demonstrates that competition for active sites (anions or DCF) and formation of multiple photoproducts resulting from synergistic interactions (between both APIs) are key to the TiO2-photocatalysed NPX degradation

Preliminary study on zinc removal from aqueous solution by sago wastes

In this study, sago wastes were investigated for its potential in removing Zn from aqueous solution. The equilibrium adsorption level has been studied under varying conditions of time, initial metal ion concentration, adsorbent dose, particle size and pH. The adsorption parameters were analyzed using Freundlich and Langmuir models. Kinetics of adsorption of Zn on adsorbents were determined and correlation relationship between kinetics of Zn adsorption and with pseudo first order and pseudo second order rate was determined. The physico-chemical properties such as determination of functional groups, moisture content and ash content were also investigated. The adsorption of Zn increased with increasing treatment time and the equilibrium of the adsorption was attained after 40 minutes The data showed that at initial concentration of 5 mg/l, the percentage of Zn removal based on the particle sizes of 300 µm, 500 µm and 1200 µm are 74 %, 47.6 % and 55.4 % respectively. The percentages of removal increase after the initial concentration of Zn reach 40 mg/l to 100 mg/l and the percentage of Zn removal based on the particle sizes of 300 µm, 500 µm and 1200 µm at 100 mg/l are 6.93%, 7.78% and 10.03% respectively. The study shows that the adsorption gives an optimum value at pH 9, best fitted on Langmuir isotherm model with maximum capacity of adsorption of 10.4 mg/l and obey the pseudo second-order rate equation of adsorption kinetic. However, at pH 7 which represents the normal pH range in wastewater treatment, maximum Zn adsorption is only 0.45 mg/g. It is recommended that further complimentary study should be conducted, for instance the sago wastes should be modified chemically in order to further enhance the removal of heavy metals from solution

Combined effects of adsorption and photocatalysis by hybrid TiO<inf>2</inf>/ZnO-calcium alginate beads for the removal of copper

The use of nanosized titanium dioxide (TiO2) and zinc oxide (ZnO) in the suspension form during treatment makes the recovering and recycling of photocatalysts difficult. Hence, supported photocatalysts are preferred for practical water treatment applications. This study was conducted to investigate the efficiency of calcium alginate (CaAlg) beads that were immobilized with hybrid photocatalysts, TiO2/ZnO to form TiO2/ZnO–CaAlg. These immobilized beads, with three different mass ratios of TiO2:ZnO (1:1, 1:2, and 2:1) were used to remove Cu(II) in aqueous solutions in the presence of ultraviolet light. These beads were subjected to three cycles of photocatalytic treatment with different initial Cu(II) concentrations (10–80 ppm). EDX spectra have confirmed the inclusion of Ti and Zn on the surface of the CaAlg beads. Meanwhile, the surface morphology of the beads as determined using SEM, has indicated differences of before and after the photocatalytic treatment of Cu(II). Among all three, the equivalent mass ratio TiO2/ZnO–CaAlg beads have shown the best performance in removing Cu(II) during all three recycling experiments. Those TiO2/ZnO–CaAlg beads have also shown consistent removal of Cu, ranging from 7.14–62.0 ppm (first cycle) for initial concentrations of 10–80 ppm. In comparison, bare CaAlg was only able to remove 6.9–48 ppm of similar initial Cu concentrations. Thus, the potential use of TiO2/ZnO–CaAlg beads as environmentally friendly composite material can be further extended for heavy metal removal from contaminated water

TiO2/PKSAC functionalized with Fe3O4 for efficient concurrent removal of heavy metal ions from water

An effective material to assist in the elimination of heavy metal contaminants in the water system is necessary, as they persist for a long period in the environment. A novel multifarious TiO2/PKSAC/Fe3O4 composite with combined properties namely adsorption, photocatalytic and magnetic was successfully synthesized and applied for the simultaneous removal of mixed heavy metals, Pb(II), Cu(II), and Ni(II) under various conditions. Characterizations confirmed the fabrication of TiO2/PKSAC/Fe3O4 composite. An optimal adsorbent dosage of 0.9 g/L allowed >80% removal efficiency in 10 ppm of mixed metal ions solution. Among all three catalyst ratios, the equivalent mass ratio of 1:1:1 (TiO2/PKSAC/Fe3O4) demonstrated the best performance (>72%) in removing Pb(II), Cu(II), and Ni(II) ions, even after the addition of coexisting ions (Ca2+, Na+, Cl−, Br−) during the treatment. A recycling study confirmed the materials' regenerative stability. The fabricated TiO2/PKSAC/Fe3O4 composite can be applied as an effective material for heavy metals removal in wastewater

Removal Efficiency of Ammoniacal Nitrogen from Palm Oil Mill Effluent (POME) by Varying Soil Properties

Palm Oil Mill Effluent (POME) contains large amounts of organic matters and nutrients. Instead of discharging into oxidation ponds, POME can be used as an alternative option to replace inorganic fertilizers which have been known to increase the hardness and acidity of the soil over time. This study investigated the effect of different soil properties on the ammoniacal nitrogen removal efficiencies in POME. The ammoniacal nitrogen removal efficiencies from three mediums over 7 days of retention times were studied. Medium I contained major amount of sand, whereas medium II contained major amounts of clay and lastly medium III contained large amounts of silt and clay. The results showed that medium II produced the highest removal efficiency of ammoniacal nitrogen in POME, with the average removal efficiency of 77±5.1%. The average values of removal efficiencies obtained from mediums I and III were 61±6.2 and 58±11.3%, respectively. In addition, the removal efficiency of ammoniacal nitrogen increased slowly with the retention time. Medium II recorded the highest removal rate (k = 0.0897 dayG1) compared to mediums I (k = 0.0435 dayG1) and III (k = 0.0492 dayG1). The mechanism of removal ammoniacal nitrogen from the medium occurred via absorption by the soil particle

A highly photoresponsive and efficient molybdenum‑modified titanium dioxide photocatalyst for the degradation of methyl orange

The degradation of azo dyes in aquatic environments is still challenging due to their stability and perpetual effect. This work demonstrates the application of highly ultraviolet-responsive titanium dioxide/molybdenum photocatalyst to degrade methyl orange. A series of titanium dioxide/molybdenum photocatalyst with different molybdenum concentrations (1–10 wt%) were synthesized by a facile wet impregnation method. The introduction of molybdenum has favorably induced changes in surface morphology, crystallite size, optical absorption, and specific surface area, which have collectively enhanced the photocatalytic performance of titanium dioxide/molybdenum photocatalyst on the removal of methyl orange. A systematic investigation on the influencing parameters such as photocatalyst dosage, initial methyl orange concentration, and initial pH was investigated, and the optimum conditions were achieved. The best-performing titanium dioxide/molybdenum (3 wt%) photocatalyst yielded a 94.5% methyl orange photodegradation efficiency within 120 min of irradiation. The dopant concentration, photocatalyst dosage, and pH were investigated to validate the optimized conditions for titanium dioxide/molybdenum on methyl orange removal using response surface methodology via the Box–Behnken design. The present results demonstrated that both the superoxide radical and hydroxyl radical play a primary role in the degradation mechanism. This study provides fresh insight that the successful structural modification of titanium dioxide by molybdenum could enhance the photocatalytic removal of dye wastewater

Titanium dioxide photocatalysis for pharmaceutical wastewater treatment

Heterogeneous photocatalysis using the semiconductor titanium dioxide (TiO2) has proven to be a promising treatment technology for water purification. The effectiveness of this oxidation technology for the destruction of pharmaceuticals has also been demonstrated in numerous studies. This review highlights recent research on TiO2 photocatalytic treatment applied to the removal of selected pharmaceuticals. The discussions are tailored based on the therapeutic drug classes as the kinetics and mechanistic aspects are compound dependent. These classes of pharmaceuticals were chosen because of their environmental prevalence and potential adverse effects. Optimal operational conditions and degradation pathways vary with different pharmaceutical compounds. The main conclusion is that the use of TiO2 photocatalysis can be considered a state-of-the-art pharmaceutical wastewater treatment methodology. Further studies are, however, required to optimize the operating conditions for maximum degradation of multiple pharmaceuticals in wastewater under realistic conditions and on an industrial scale

Recent progress of Ag/TiO2 photocatalyst for wastewater treatment: Doping, co-doping, and green materials functionalization

Surface modification via doping or functionalization is one of the most commonly applied approaches for addressing the innate limitations of TiO2 photocatalysts. Amongst numerous dopants, silver (Ag) has been regarded as an efficient strategy to retard electron holes recombination due to the formation of the Schottky barrier on the TiO2 interface and extending absorption to the visible region. This review primarily focuses on discussing and evaluating the recent progress in the modification of Ag/TiO2 via co-doping with non-metals and transition metals, as well as the synthesis strategies that have been applied in engineering the materials. The effects of doping and co-doping on the induced chemical and physical properties, photocatalytic performance, stability, and recyclability aspects have also been highlighted. This review also examines the potential improvement of Ag/TiO2 through the addition of green materials such as plant-based materials (cellulose-derived composites, chitosan, alginate), ceramic materials (clay, kaolin bentonite), and also ionic liquid green solvent. Recommendations for further research opportunities, limitations, and challenges have also been suggested